The guy I'm seeing had sex with another girl. What do I do?

I’ve been seeing this guy for about a two months now. He’s “wanted me” for about six months and at first it was just lust on his part. I didn’t have any feelings for him then so I rejected him, but recently we’ve been getting really close and it’s turned into us both liking each other.

As a result, we’ve been seeing each other for a couple of months. We text everyday, we flirt, we act like a couple, everyone’s labeled us as a couple, we snuggle in bed, fall asleep together at least once a week but not every night (because we’re both busy with work). At first we were just mucking around in bed but last week I lost my virginity to him. He’s had sex with a handful of other girls but he is responsible and will always own up to it. Although he was the one who suggested having sex, he was very hesitant because he says he doesn’t want me to regret it and because he can’t promise me a relationship as he doesn’t want me or him to get hurt. Hence why were not in a relationship.

The other day I was out of town for a night for a business trip with my boss’s son who is around the same age as me. We could’ve easily hooked up but we didn’t because I wasn’t interested and we were both pretty busy with work anyway. When the guy I was seeing found out I went with my boss’s son, he kept asking me if anything happened and seemed pretty upset about the fact that I was with another guy for the night and we could’ve potentially did something.

That same night he went on a pub crawl and got pretty smashed. He had trouble finding his way home so he had to stay over at one of his girl friend’s houses. This girl claims she wants him to “father her children” but he says he doesn’t want her.

He called me and told me that he was safe and at her house because his phone had run out of battery and he couldn’t call a cab. He told me that by the time she came back with a charger he had passed out on her couch. He said he really needed to get out of her house and asked if anyone we knew could pick him up and I did.

I saw him later that day and he told me that story once more and I believed him. A couple of hours later a friend of mine who he had been talking to earlier called me and told me that he had had sex with that girl the night before and that he told her himself. Five minutes later I get a text from him saying “whatever they have been telling you don’t believe them. She came up on me but I stopped it”.

I don’t know of who or what to believe. I know we’re not exclusive, I know I have no right to be upset or pissed, and I’m not really. But I just don’t know of how I’m suppose to feel right now, and if I should continue seeing him or have sex with him again… Forgive him because technically he didn’t cheat on me. I don’t want to be used for sex and I can’t help but wonder if we could end up in a relationship despite him not being ready for commitment.