husbands past

I'm so insecure of my husbands past that I think it's ruining our relationship. He has never been faithful to anyone in his whole life. He was married before for 8 years and cheated on her the whole time. I just can't get past it. He has never done anything to me though. He has changed so much, he is older now and he just doesn't want that life but I for some reason cannot trust him. Idk what to do and at this point just need some advise.