<human>: Can you summarize the given text in a few sentences?

Found out about 9 week ago he sent messages to an 18 y/o that he wanted to get drunk with her on school grounds and might end up naked.

He promised me he was being stupid and he'd stop - I (f.21) believed him despite me not being able to trust him still. 

I checked messages 4 days ago, I shouldn't have but I literally can't trust him and I found him offering to bring her stuff for a hangover and 'cuddles'.
I pulled him up about it, this time instead of admitting he fucked up he said it was just friendly he didn't know it was a line to cross.

We were at a dinner thing and I saw a text from her flash up - nothing serious, but he went to the bathroom and came back. I said to him his phone beeped. His response?

"I don't possibly know who could be texting me." pulled him up for lying and he's promised to never text her again.

We'd be 2 years in May.

Sorry for grammar etc, on phone, upset.
<bot>: BF (23) kept texting 18 y/of after 2 occasions of inappropriate texting.  I now can't trust him, I'm utterly destroyed but still love him.