idk if anyone can give you mixing advice because chances are your hearing something completely different than what we're hearing because your not using proper monitoring equipment.
it's never too early to start good mixing practices, so here's my headphone recommendations for mixing sorted by price range, idk what kinda budget you'd have for this
Audio-Technica ATH-M20x ($50)
http://www.sweetwater.com/store/detail/ATHM20x
never mixed on these, but have compared them to their older brother the athm50x which I mix on all the time and they sound pretty damn close in quality, but if I had a limited budget I'd go for these.
Sennheiser HD 280 ($100)
http://www.sweetwater.com/store/detail/HD280Pro
used these when getting my certifications for pro tools, mixes translated pretty well from
headphone to monitors.
Audio-Technica ATH-M50x ($150) http://www.sweetwater.com/store/detail/ATHM50x
my favorite headphones for writing and mixing, note tho, highs can come off a little metallically which can make the highs sound higher than they really are, its not a problem just as long as your aware and test the mix on multiple other devices every now and then.
Shure SRH1440 ($300)
http://www.sweetwater.com/store/detail/SRH1440
while the ATH-M50x's are my favorite to mix and write, these headphones sorta feel like I'm looking at the mix with a magnify glass, and tweaking and perfecting little mixing errors. note these are not fun headphones, they are very flat and honest.