What would be the best thing for me to do?

I really love this man and I don't think I want to leave him. I'm not so sure how much he loves me, though I think he does. We are from very different culture, background, & really different personalities. He's very moody and can be absolutely adorable at one moment and really freightening the next, even though he might not mean it. That makes me feeling more and more troubled and unsecured. And a lot of times I don't think he's considering about me so much. He has gone through a very painful divorce & his 2 daughters are living with the mother. He talks a lot about his ex-wife and his daughters. I'm more disturbed at the moment as his daughters are visiting him and I can see how much love he has for them. He's still very nice to me and I really like the two children, but I can't stop feeling that I'm putting myself in a world that I don't belong to. I'm not sure whether I can feel better in the future. I'm becoming really doubtful but I still can't decide what's the best thing to do.