I'm deserate for insight! Please help!?

ok me n my boyfriend of a year had a bad break up a couple mths ago...it was so bad tht I ddn think we were getting bak together..we broke up for like a wk..before the break up he had never cheated on me...i initially tol him I was done with him because he was ignorin my calls n txts n telln me to give him 3 days to think about if he wanted to b wit me. I couldn't take it. It was killing and hurting me. So I jus ended it. Well he tol me tht he slept wit his x durin the break up..he said he had no intentions. He jus needed a friend. He regrets what he did. Says tht he loves me and he puts it on his life. He wants to marry me. He says I'm the best thing for him n he wil do whatever it takes to get me bak. He said tht nite meant absolutely nothing. He is in love wit me. What to think of all this?