I don't know what to do.

I feel like my fiance is hiding something from me. I truly believe he was married to his ex girlfriend and he just won't tell me. I wanted to get married this past year but he kept putting it off and I think it's because you have to put your previous marriages on there. And also (it's my own fault) but I was creeping on her Facebook and there was an old picture of the two and it definitely looked like a wedding photo. I'm just so afraid of asking. I've thought about asking my mother in law but I don't want her telling him I asked.