Cheating boyfriend?

[Casey]

I have been with my partner for 8 months, him and his wife were together 17 years in total, married for 5 years. I love him very much but i often feel very insecure as he had an affair while he was with his wife and cheated on her in the past a few times. He told me he never truly loved her and he just felt trapped as they have two children together, this is no excuse for an affair in my eyes. They were always breaking up and then getting back together. I know everyone has a past but this makes me feel very worried that he will do the same to me. Any advice?