i found out my best friend might of cheated on me when we were together?

My best friend who I met in October 2013 dated from the last week of October 2013- February 2014. However, we remained best friends and I thought it worked out until now. You see, I was told by our mutual friend who knew my best friend longer than me that he still has a relationship with his high school girl friend. He caught them making out at the mall on 3/17 which ironically my best friend told me he couldn't go to our college to do homework because he had to go to "work". Instead he was at the mall making out with this girl, yet our mutual friend caught him, but didn't say anything. My best friend and I have 2 classes together and are in the same major. I then proceeded to ask our mutual friend if he had relations with this girl from October 2013- December 2013 and he told me they did. So basically he was cheating on me. Which today my best friend told me he didn't want to have a relationship with me because he didn't want to hurt me by cheating on me and that he values our bestfriendship (if that is a word), which clearly he did cheat when we were dating even though we weren't officially a couple ( but we did make out and he took me on dates where he paid)

what should i do? what should i say? i don't want to keep this in me any longer. i feel like everything he says is a lie now. i don't know if he meant it today that he values our friendship. i don't know if he really cares about me like he said he said he doesn't want to cheat on me and he truly cares about me that he doesn't want to hurt me, yet he did according to our mutual friend... :/ i don't know what to do. I already texted my best friend saying we need to talk and he better not lie to me or i will be extremely upset and mad. he lied to me to get out of doing homework, he lied to me about going to work, he lied to me when we dating but not officially a couple, clearly we went out though. he really lied and i don't know what to think, i feel so hurt.

So, I'm a tiny bit fuzzy on the details here. Firstly, the way you describe it, it sounds like you two were just dating, but not necessarily "exclusive" at the time. Is that correct? I ask because if you were really just "dating" at the time, then I don't necessarily know if that is cheating, exactly. If there was any reason to believe you two were specifically an item, then maybe I would say that it would be considered cheating.

Now, another question, he had a girlfriend when he was going out with you? Did I misunderstand you, or is that what you said? Because if that is the case, then he cheated on her with you, not vice versa. I imagine you didn't know that at the time, though. Doesn't make it any less wrong of him to do to you, though.

If you two are truly just friends at this point, it may be a bit of a moot point. Still, I must admit I don't know if somebody who could cheat on their significant other is somebody I'd want as a friend anyway.

So, bottom line, I'm not sure I am fully understanding your story. If you can clarify, I may have more thoughts on the matter.

Agreed. Personally, I would always be reluctant to trust somebody who could do something like that. A) If they've proven themselves capable of doing it once, they'll probably do it again. B) If they've proven themselves capable of doing something so horrible, why would I trust that wouldn't do other things that are equally terrible.

Hence why I would personally have second thoughts even being friends with somebody who has done something like that.