falling for a guy who doesn't like you back

i like this guy who is actually younger than me, and i find myself doing the stupidest things to get his attention and then regretting them. after liking him for a while now i realize that he is getting close with a girl i know who did this same exact thing to me before, and now i hate her even more than i already had.

i thought that he liked me too but now it's getting more obvious that that's not so. but my problem is i have no idea how to get over this kid and its stressing me out, what should i do?