Why do i feel insecure??

Sometimes I find myself thinking about ways in which my boyfriend might cheat on me. We live together and if he goes out with his friends I sometimes call to see if I can hear a girl's voice in the background.When he goes for lunch at work I wonder if he meets up with someone or if he comes home more than 30 minutes late I worry myself sick and I ask 20 questions just to see if I can tell if he is lying. I get so worked up that I get stomach pains and vomit.I've never caught him doing anything but ever since we got together I have just got it into my head that he was going to 'play games'.
I wonder if my past is making me think this way or what I've seen my parents do to each other. I asked him last night if he really loves me. Of course he said yes but I just sit and think well does he really?He does everything for me and he is so nice; How do I get over this fear in my heart and in my mind?I also tried to trick him by saying that someone told me things that never really happened but obviously this did not work.
I really love him – and hoping he feels the same way and I couldn't ask for a more considerate partner. I really feel he's my soul mate..