Husband's premarital life bothers me?

I grew up in a very very traditional Eastern culture n religion that valued virginity. I've only been with one man (hubby) in my life because I wanted it that way. Unfortunately, my husband who's an American has been with a couple of women before we got married. He said he feels bad about it, wish he hadn't done it and apologize. I do understand the different culture we grew up in. I can't force my morality on him. I love him dearly but his past is just bothering me so much. For some reason it hurts me... Why does it hurt me so much? How should I get his past out of my mind?