Do I do things to intentionally hurt myself?

I always had this crush on a guy, but he always had the same girlfriend. Last year, we saw each other randomly & he told me he broke up w/her. We started dating really quickly & were soon together. He told me he was completely over her & would never get back together with her. I was always suspected this wasn't true. Well, 1 day, he sent me a text (while I was at work) saying he still loves his x-gf and they were getting back 2gether. Recently, he sent me texts saying "could you ever forgive me, I am so sorry, I miss u, would you reconsider getting back together?" At first, I was admament, saying absolutely not. Then last week I had a horrible date, and felt desperate, so I ended up calling him and we hooked up. Now we are talking again, and I can see myself falling back into the same habits. He has told me the same things about his ex, saying this time they are completely over, but I still can't really trust him. Am I absolutely insane? Am I just setting myself up to get hurt?