Ok, a week ago my fiance of two years broke up with me because he likes another girl, but he loves me, and he can't pick.
Next thing I know, he is dating this girl.
He's liked her for about 8 months now.

He broke up with her for me, and we got back together.

Then, he broke up with me again, saying he still couldn't choose, but he agreed not to go out with her or kiss her, and just take some time to think.

Then today I saw them kissing outside the mall, and I lost it. I kicked him and punched the girl. He lied, I was angry.

Then I realized what I did and knew I had no chance of getting him back, and that destroyed me.

I brought everything he'd bought me back to his house, and tried to leave. He didnt want me to. Said he likes her, but loves me. Wants a break to just be friends and strengthen our relationship before getting married. Says he won't date or kiss the girl, and broke up with her via text while I was there.
He did cry, however, because he was giving up a girl he likes so much, but told me I am worth it.
I told him I am worried he is going to be with her anyway, and he said "well i cant promise i wont slip up, should i just not tell you if i do?". i didnt answer because weve had that fight three times this week, and he knows thats not okay.
We left it at: he wants this break to strengthen our relationship so that we can become stronger, but we are not dating, so no kissing or touching. He does want to be with me someday, he is 99% sure.

I cant lose him...
Does this sound like an excuse?
What can I do to get him to want me back, and only me? Just give him the space?
He just wants me to stop worrying so we can have a relaxed relationship again, one that will work out, rather than this constant worry..or so he says. please help!