Please help me to help myself

So my son's father and I broke up earlier this year briefly. It resulted in him getting another woman pregnant. He hid it from me until a family member of his unknowingly told me about it. I was angry and extremely hurt. Although at the time we weren't it still stung my heart. So the baby has been born and it hurts even more. Well he said he wanted to tell me but didn't know how to. Plus he was leaving to the military and wanted marry me but not with this secret over his head out of fear I would divorce him. Well after not speaking to him for month or so while he was away at training he came back for the holidays.We spoke and he said he still wanted to marry me. That same day we spoke we got married. The next day I felt like crap because of everything between us. He says he didn't want to be with the mother to the baby and put himself in a bad spot but accepts what he did and wants to move forward. I feel like he married me just because and may want the other woman down the road and regret it. What can I do to feel secure? How do I get over this? What should I expect from him? I feel like a fool for staying but the other part feels like we can Make it through.