Husband spills the beans and tells me TMI about his past life!

My husband got really drunk at our vacation last week and I pregnant and stone cold sober! When we were in bed he tells me about a blond haired blue eyed girl that would visit him while we were dating and give him oral sex and he admitted to sleeping with her. This information makes me really sad and I know we were not married but we were dating exclusively! Do I just need to let this go...it seems now that I have a ton of questions and I am doubting his loyalty during our marriage!