Dumped

My boyfriend broke up with me last week, & he hasn't stopped talking to me since, he wants to be friends but I still love him & want to be with him.. Friday night I tried to get back on my feet & it failed. Saturday I went to a party to have fun & forget, I posted a picture with a guy friend, so he called me concerned & offered to come get me so we could talk, drunk I said yes we had sex & he went to the restroom I checked his phone & found messages to other girls trying to hook up.. I've never seen this side of him ever.. & he admitted he hooked up with someone but he won't tell me who.. It's killing me & I need to know.. Any advice about that or the situation in general? I'm so devastated.