Boyfriend's past

What would you do if you found out your boyfriend had sex with a man? boyfriend told me he had only had anal sex before meeting me. I thought that was a little weird seeing as though he said the person never had sex before either and just wanted to do anal...I asked him if it was a guy, he told me no. Come to find out it was in fact a male. He didn't tell me, I found out on my own. What would you do? Side note: I have no problems with the lgbt community...it's mainly the fact of him lying about it to hide it from me.