new relationship help!

I met this really great guy but he is separated from his wife they are in the process of going thru a divorce they have 3 girls together. He is still heartbroken over her he's told me he has tried to get back with her in the past and she doesn't want him back . They've been split for a year before I came into the picture. So we've been sleeping together for about three weeks to a month and I'm falling in love with him and I let it be known to him how I felt only for him to say that he feels we are moving too fast and we need to slow down which I agree with him. But how do we do that and not push each other away? I also feel he may be using me as a crutch and I don't want to get hurt either what do I do?? Any and all please advise