hey im 28hh and 5'4, i feel u. not to mention how expensive small back big chest breasts are. lose some fat if you can be bothered if not wear flattering clothes like stuff from bravissimo, they have coats, shirts etc. also sell supportive swimwear, idk about their sports bras, never have found any that work. maybe try lifting to even out your physique then it wont feel so much. tea dresses or whatever are really nice for me, they fit under your bust and are flat against your tum and fitted to your waist. bodycon and tightish tops. maybe try building your lats or shoulders. im a couple years older so ive had several years of trying to become apathetic to my chest. embrace it, accept it, forget about it. it doesnt matter and worrying about body issues is such a waste of time. they are just boobs pal, everyone wants something else.
also if u want me to link u to some nice bras, swim stuff, clothes etc etc lemme know.