Is He Cheating?

Okay, if anyone reads this and has an opinion, feel free to weight in.

So a little bit ago DH started talking a little random and crazy, I think he's starting to "flash". So he's talking to me and all of a sudden he calls me some other chick's name! It's a long story but he's friends with the boyfriend of this girl's sister who also is one of his friends ex-girlfriends. They all live together so he sees her a lot. Of course I called him on it right away and am still blown away that it actually came out of his mouth. As soon as I did he immediately got defensive and said "it's not like you've never called me out my name". Uh, NO I haven't and if it was it was our kid's name, not some random dude. O M G I don't even know what to think right now.

So what would you think? Random slip of the tongue or something more sinister? Even if it was just an accident, if he's only going over there to see his friend, why is SHE on his mind? I think something's fishy...