Insecure??? Not Me..... Or Am I?

I have been with my boyfriend for 8 months ... And over all our relationship is wonderful. I really love him a lot and actually see a future with us. He is 10 years my junior, as I am 30. He is a young black man who is very nice loooking and has a great personality.... The problem is, I am very insecure when it comes to him. Ive never been jealous or insecure in any previous relationship. He doesnt actually give me any reason to be insecure, other than when we first started talkin, he did have a girl, but ,i also had "friends". I never meant for our relationship to grow into what it has. And now, I cant imagine my life without him. But, I dont ever want thim to be away from me cause im afraid he is gonna find a younger, prettier woman . I try to do everything I can for him. And when I ask him about other girls, he says things that I do , most females wouldnt. But, to me those arent reasons he is with me. I try to please him in every way I can. But, sometimes, I feel it isnt possibly enough. I am drivin my self crazy everyti me he leaves... Thinking he is going to be with another female. But, he promises me he loves me and he isnt doin anything wrong. I want to believe him and I want to get past this.... What is wrong with me??