I've never posted on this board before but I really need some advice/comfort.....

I dated this guy for 8 months, and last week I told him I wanted to take a break, for many reasons, one of which is I feel like we're too serious, and i'm in college, I want to have fun...He tried to convince me not to take a break and he got kind of upset that I suggested it.

And then, this morning, I found out a few things accidently:
- he slept with his ex like 2 days before we started dating. And he never told me about it.....Before when I asked him about what happened that night he said nothing and that he just passed out.
- a few times when i've been out of town, he's been drinking and he's told his ex to come over to hook up. He even told her shes hot and just as pretty as me.

I don't know what to do, I haven't talked to him today since i've found out about this stuff, and i'm not sure what I want to say. We aren't really on a break, we're sort of still together (for now)..But being around him has felt so weird and just not right lately. He says he loves me and would never hurt me, etc, but I feel like our relationship has been based on lies. I dont know what to do, please someone give me some advice!