I became friends with him, and about four months after we became friends (and after four months of me liking him and him having no idea)
He found out, and I found out that he'd always had a thing for me.

It's a year later, the next Halloween just passed and we'd been going out for eight months. The longest relationship I've ever been in (same goes for him) and we'd been through a lot together.
Abortion, friend problems, family problems etc
I opened up to him about things more than I have to anyone who is not family, and told him things I've never told anyone. Serious things.
I love him completely.

BUT, I found out that on the most recent Halloween he cheated on me with the girl he was with when I first met him (who I'm supposed to be amazingly good friends with)
There was a lot to it, but basically they both said that they just made out all night. And he claims he cannot remember anything.
So, being the push over that I am I just tried to let it go and didn't make a huge deal of it.
But I couldn't stop thinking about it, and it was absolutely tearing me to pieces so I told him that we need to go on a break.

(Which is breaking my heart, because all I want is to be able to forget it ever happened and be able to kiss and be with him)

Last night, after avoiding her phone calls since Halloween, the girl staid over at my house. And I found out that he not only made all the first moves, but he also convinced her that I was okay with it, and fingered her.

I'm a complete and utter mess. He's been sobbing every time I've talked to him, and says he'll do anything to get me back..
But I don't know what to do.
If I get back with him I'll be a pushover, but if I don't I'll be miserable.
I never thought he'd do something like this to me, and honestly love him so much. It's unbearable.

Is there any advice anyone can give me at all?
Please?