BOYFIREND HELP!!!!

Well, I have these boyfriend that I been going out with for 2 month`s. He is 18 years old and I`m 15 years old. We been having sex without a condom, but every time when he is about to *** he moves. One day I asked wut about if I came out pregnate? He said that he will be there for me and the baby. And he saided like in a serious way. We started talking about that because I had told him that I haden`t had my period that month, I was gettin scare and I had to tell him that I was probably pregnate. I told him that if I was that I was going to move out to a far place that nobody will find me and that I was going to come back when I had the baby already. And he said No, that he will never let me do that, that he want`s to be there for my pregnacy because that was his baby. And I kind of believed him. Lately these day`s we been having alot of arguement`s that I come up braking up with him. And every time that happend`s his alway`s begging me for another chance. And his that kind of guy that supposly never beggs girl`s and all that gansta stuff. Once I got to go out with him, he was another different guy. I dont really understand him. Every time we brake up he says that he would change and all that, but once were back together his thae same. SO PLEASE GIRL`S, NEVER BELIEVE THEM GUY`S THAT SAY THEY WILL CHANGE CAUSE THEY NEVER WILL. Right now I`m still with him, but I dont know what to do. Can you PLEASE HELP ME?????