I dont know what to do.

hi, so I was in a relationship for 4 years off and on, (mostly on) and then he developed a drug problem. I had told him a few times when we were still together if he does not stop im going to leave. he didn't stop, so after a year from when I noticed it started I left him. after I left he told me that he was wrong and hes sorry and all that. but also that he made me feel like biggest piece of shit for asking what he was doing and trying to help him. Everyone says im better off with out him but I cant help but love and miss him after what hes done to me. before the drugs everything was perfect. he moved out of the house he was at that had it and he says hes clean but im already with someone else. But im afraid that I don't love the one im with as much as I should because I still miss kind of love my ex... so should I leave the one im with and go back??? or stay with him???

I miss what it was, what we were, all the dreams, hopes, ideas we had together. He was there for me for 3 years, before he got into drugs. I miss what we were. I still think of him everyday hoping he's ok. he knows so much about me. I don't like hurting people so I feel kind of bad for leaving and being with someone else. he wont talk to me anymore and I kind of want to talk to him, if anything just to settle what was wrong and still be close friends but I think I hurt him to much to do that. The day I found out he's been lying for a year, its like my heart just shut down if that makes any sense. today I was even thinking of breaking up with who im with because im afraid I guess. kind of feels like I don't know what love, trust, or truth is anymore