What's your setup for tracking, mixing, equipment, DAW?
Is does sound pretty thin and light...just my opinion.
No body or fullness to anything in the mix.
A well treated room with good monitors?
What brand of headphones?.....they lie ya know...they can't give you adequate bass and most are not very flat.
Good for tracking, general listening of music or to focus on some mix detail....great, but not for mixing.

Headphones are sennheiser hd280pro, monitors are krk rokit 5, mic is rode nt1a, fast track usb and fl studio with omnisphere, mostly

room treatment is as far as the clothes lying on my floor... though that is wont to change any day now lol

The simple answer is you have to have a proper room and aligned monitors to listen to your mixes in.
Good monitors are designed to be flat from Xhz-Yhz and they are tested in a lab room space. So that means that no matter what frequency you put into them the levels of all those frequencies will be within say +/-3db. Relatively perfect right!?

But as soon as the sound leaves those cones, they will only produce that perfect flat level sound in the same flat treated room where no one frequency is booming or weak or cancelled out by something else like your reflective walls or clothes on the floor or the window behind you or something trapped in the corner of a square box. It just doesn't work. Without an accurate room your just listening to some speakers in a room....might as well use PC speakers.

If the room has no treatment and hasn't been measured for response, then you can't trust the levels or the accuracy of anything your hearing in there. You can't use one without the other. It requires two parts of that equation to be of any use. You have to be able to hear the levels of all those frequencies accurately. Having $5000 monitors doesn't mean a thing.

When you build a room that's flat and quiet and you sit in the sweet spot of your two properly aligned monitors everything will "sound" exactly how you recorded it in all it's detail. You will be able to hear and adjust levels and know which one sticks out or is too quiet, EQ, pans, reverb's etc....everything will be there exactly how it really is. Just like any commercial record is mixed and created. And it will sound exactly the same no matter where you play it or what you play it on and if it sounds thin and muddy in your car you'll know it's not the recording it's those speakers in the car that sound like junk. Your room and your monitors become your reference.
So nothing you are using right now to "hear" your music is accurate enough to believe its mixed right and you have no way of telling that one way or the other.

OK so for now until I've got a few grand lying around I'll mix with headphones and use the speakers for folding laundry :)

Yes,
It's a tale you've heard many a time before...
my song sounds great (to me) in headphones, but thins out to hell on my monitors.

Translation.

exactly.

I can tell you have a good ear but I can also tell your room or something, is producing low freq that are effecting how you mix. You are hearing artificial bass created in your room, not your mix. Your mixes needs more bottom end but if you did that in your room, it would most likely sound way to bassy to you. make sense?

Another way of looking at this. If you are painting a picture and you have a pair of pink sunglasses on, everything you see with have the colour pink in it, right? So, you most likely will always avoid adding any pink in your picture. But how will everyone see your picture if they aren't wearing the same pink glasses? We will all be wanting more pink! So the way your studio is right now, you are not hearing your mix accurately. You can learn to get it better if you know what your room is doing to your sound. But what a nightmare. You are always guessing.

Your room is producing way too much pink (bass) so when we hear your mix, the pink (bass) in missing. Got it? This goes for your monitors too. If they have poor high end, you will most likely mix with less bass in your mix.

You're all wrong. Sorry to put it that way but... your vocal is lackluster for a number of reasons. Firstly, your room and your monitors are causing you some severe standing waves and bass cancellation. Your vocals are in fact muddy due to a lack of high pass filtering. It sounds great in headphones, I know. But that won't translate well to speakers which it ain't doing. So here's what you do... first, high Pass filter i.e. roll off some low-end of the vocal because it's not thin. It's just the opposite because your speakers are screwing you up. Once you have high pass filter your vocal you're going to crunch the living crap out of it with compression. You don't want a fast attack time but you do want a modestly fast release time. This will bring up its apparent loudness level but keep it in a place where you can place it within the mix and have it sit consistently. I don't hear any terrible acoustical aberrations utilizing your sophisticated clothing bundle acoustic absorbers? And if you're not happy with the room's acoustic signature on your vocal, that's where downward expansion and/or gating can make all the difference which is also possible to do in hardware or with software. Gating is really electronic acoustic control. Utilizing absorbers, bass traps is largely a bunch of bunk that acoustic engineers make their living with and then everybody else thinks they need to have for recording purposes. It's more applicable to your control room monitoring purposes than to the recording side. I have to deal with that at all sources different live environments on location. That's where having a consistent and controlled monitoring environment is crucial. The recording environment, not so much so when it comes to pop music genre recording. Not true with fine arts/classical music where the acoustics of the environment play a key role in the sound. Your stuff is all mostly electronic with only your vocal being the only acoustic recording you are making. You're not even singing out loudly so the acoustic environment really has not much to do with your vocal recording. So it's really a simple fix in your mix. It's easy and you'll love the results. Conversely, if you'd like, solo your music track and post it. Then solo your vocal track and post it. I'll do what I described and you'll understand when you get it back from me. And the same technique that I'll utilize I also utilize in other acoustic instruments in pop music recording. That's where noise gates and downward expansion makes all the difference in the world. And then you create your acoustic environment electronically with software, digital reverb and effects processors and voilà. That's what they're made for. They can be utilized as effects or acoustic generators.

One of the other factors in your monitoring can also be whether you are utilizing passive or active monitors. With passive monitors and separate amplifiers, you have the ability to invert polarity. We're not talking about reversing phase which has to do with a left right situation. With active monitors, reversing the phase to both is not quite the same as reversing the polarity to both. I've solve numerous control room dilemmas from the former owners of API's own studio to edit suites at NBC-TV and others. And that was from reversing polarity from the amplifiers to passive speakers. With active speakers it becomes more of an acoustic dilemma in your control room because of that limited option. I've even considered opening up some active monitors to reverse polarity of the speakers within the active monitors for both monitors. It all depends upon how the manufacturer conceives how their monitors should sound. So I understand what you are going through, fully. Now you do to.

I like simple fixes... like a single malt scotch.
Mx. Remy Ann David