My husband. Help please..

Okay so I have a tricky scenario.. 
We've been together for a long long time.
Lots of Love, lots of trust. 
There were a few way minor incidents in the past where like a random boob picture would be saved on his computer and he wouldn't remember (or is embarrassed) saving it. And it's his ex so I assume it's old but it could be new. That's possible. 
So here's what happened..
It's his birthday and I threw this HUGE party for him after an amazing spa day and basically best day ever. And it was all a surprise. 
I'm sober, everyone is crazy drunk.. One of his best friends is my best friends boyfriend and she suspects he's been cheating on her with a coworker but can't prove it. So as a good friend..  He's black out and I borrow (ha sorry guys) his phone. I search into the message area the word "cheat" to see if he spoken to anyone about his cheating.. Well there some random texts but there's one from my husband. 
It's talking about this girl who was so hot oh my god unbelievable was flirting with him and came up to him. She sat in his lap and loved on him a little but didn't kiss him. She grabbed his dick and send a text from his phone to hers so she'd have his number. THis is all what my husband is telling his buddies, so then he says she texted him and he felt guilty and told her that as much as he'd like To fuck her brains out, they'll have to just be friends.. And he knows he'll regret it 
So I read all that and I'm in shock.. My perfect husband who hates cheaters.. So I show it to him and he crumbles, and he says he doesn't know why he did t but he wanted to impress his guy friends because they were teasing him about how he couldn't get any.. Now i want to believe him but I don't know.. He's amazing and so honest and we've never had a problem. He's giving me my space and anything I need or ask for he's giving me. If I want to look at texts or photos he does it. But I don't want to do that.. I want to know in my heart this isn't true and .. I just don't. Idk. 
He's not the cheating type, and the story did seem a little far fetched.. But crazier things have happened. So, did he cheat on me.. Or. Is it just a story he fabricated to impress his guy friends. 
Help? Please.. 
Update:: I really appreciate all the advice guys thank u so much. I love how this app brings strong confident women together to uplift each other rather than the social norm or tearing each other down. Please keep posting your thoughts, let me know what you think or your experiences:)