When I told my ex, about half way (4 months) into our relationship, she flipped out. She was like "so this whole time you have been having sex with me, you have fucked guys in the past?" I was just like "yeah. And girls. What's the problem?". She just seemed most concerned that my dick had been in a guys arse. She didn't care about other girls.
From then on, sex kinda went down hill with her, she didn't seem into it at all. That was part of the reason we broke up.