I'm so sorry to hear that. The same happened to me. But it was somewhat accidental. It was the first time he blacked out and I had seen him drunk and didn't know what to do. I tried to call his mom and looked for her number on his phone when I ended up finding messages to and from women. No smoking gun that he actually met up with them, but definitely flirty messages. Then a good year and a half later the idiot thought that if he changes the names to men's names I won't find out. I didn't even have to look through his phone because the moron leaves his phone out and has it set to preview the text message on the locked screen. I'm sorry, but if you are gonna cheat have the brain cells to make it a little discreet. I'm sitting watching TV and he's blacked out and I see the thing light up with a disgusting message to him about "last night".
Ok...let me stop reliving that. Just burns my biscuits! Glad he told you about the protection level being non-existent. Fine it was when you were on a break and maybe that was part of the understanding, or maybe there weren't "break" rules, but his biggest deceit in all of this is exposing you to disease knowingly. That is unforgiveable. If he was having sex with women unprotected and then had sex with you unprotected and told you he wasn't with anyone else, it may even be criminal.
Again...I'm not one to talk. I let him treat me this way. Don't do the same.