I need advice

So the guy I’ve been talking to has been texting my best friend. I’ve felt like they were flirting before, so I spoke to both of them about it. They promised it wouldn’t happen again. However, tonight he snatched his phone from me and deleted their conversation before I could see it. He claims they were talking about my birthday which is coming up.

Right when we started talking, I found out he was also talking to another girl. He was pissed I found out because he thought he was slick. He promised me that would never happen again.

I’ve like this guy for 5 years now, so I don’t know if I like him too much to see what’s going on. But I need advice.