My boyfriend is becoming obsessive and scary. Why?

I have moved in with my boyfriend and I have many male friends. I went to the cinema with one of my male friends the other day and when we both came out of the cinema, out of the corner of my eye I saw one a guy follow us around town, but I didn’t let on I new what was happening. I went back to my boyfriends house quite late at night, I walked through the door and through the darkness I heard him say “Where have you been?”, because my boyfriend doesn’t like me having male friends I said that I went out with the girls. Then he started bombarding me with loads of questions like where did I go, did I meet any guys etc. I just got annoyed and said “Grow up!” to him and walked ped him, as I did he grabbed and held my arm really tightly to a point where it really hurt and slammed my back against the wall. I was so scared I didn’t do anything. The he said in a tone I have never heard him talk like before “You so much as look at anyone, or talk to any guy, you’ll regret it big time do you understand?!” I was so frightened I just agreed to what he was saying; I thought for a second that he was going to give me a hiding of a lifetime, I stupidly kissed him, and that kiss turned into a snog and so on and so fourth we ended up having s*e*x. In the morning I sat up to see what the time was and he put his hand on my stomach and gently pulled me back to bed and kissed me really lovingly. Then we he stopped I kissed him and we had s*e*x again. I love him so much and I don’t want to loose him, what shall I do?