<human>: So what does any rational sane person do in an awkward social situation?  ASK IN THE INTERNET FOR ADVICE OF COURSE!  But basically here's what happened, I was out at a bar the other night and my roommate was there as well.  We drove separately however.  As the night wears on I end up going to another bar with some of my other friends until around close.  I return to the first bar and see my roommates car is still there so I enter and look for him.  Run into some other friends who want me to drink with them before close.  I do, all the while looking for my roommate.  He's still MIA.  Begin to think about earlier that evening when I saw him talking to some girl I did not know.  I decide its time for me to go home as the bar is about to close, he's car is still outside.  Confused, I return home.  He's not there.  The next day I ask him online where he ended up last night and he said his girlfriends but as I prob him about why his car was still there his story changes a little and he took a long time to respond to my questions.  Later I sparked a conversation about lying and he got SUPER awkward.  So, now I am placed into a odd situation where I think my roommate might have cheated on his girlfriend, who is an ex of mine and a decent friend of mine as well.  So what does reddit think I should do?

Condense the text into a few key points
<bot>: I think my roommate cheated on his girlfriend who is a friend and ex of mine.  What does reddit think about this situation?