My boyfriend (ex) cheated and now he wants me back helppp?

well on june 13th 2011 me and my boyfriend would have been together for a yr. so he has this ex that i just cant stand shes always there and its just obvious that she wants him back. now he knows that she likes him but he talks to her everyday and recently they have been hangin a lot so i dumped him 2 wks ago for it but i never told him wy so when i finally told him it was over her he was lik im sorry i never knew she phased you ill leave her alone bla bla bla so we got back togetha!...THEN! we had this talk about have we ever cheated on 1 another i said ive kissed a guy 1 time and thats the only time ive ever cheated! and that was during the 2nd month of us being together. he got really pissed and was just upset so i asked him "your tellin me this entire yr of us being together you NEVER cheated?" he swore up and down he didnt he was lik i flirt and chill w/ girls but to actually kiss and cheat on you noo never bla bla bla! so then 2 days later i get a phone call from some girl saying that my bf has been sleepin w/ her friend so i confront him and hes lik noo she wanted to have sex w/ me but i told her no so she had sex w/ one of my friends now i knew that was a lie so i kept tellin him if your lien just be real if u ever cheated let me know now..so finally he admits that he has cheated and he tells me everything he has done so i broke up w/ him!(to inform you guys iam a virgin so we have never had sex! and i understand a boy has needs so if im not doin it somebody else is but he shoulda just told the truth and at least broke up w/ me b4 he cheated) anyways everybody was shooked b/c everybody loves him my family and friends so since weve broke up hes been really trying to get me back and this morning i was going to take him back until i seen that he was w/ his ex that i told u guys about in the begining (i guess she had a grad. party and he went an they smoked after) so now im lik eff you and im pissed b/c your tryin to get me back but yet your hangin w/ the girl u kno i dont lik and u said u would leave her alone so im really hurt b/c i love his boy lik soooo much words cant explain and i want him back but i cant trust him an he keeps doin wrong!