My bf cheated on me

In summer my bf cheated on me in a party, he was high, but that isn't a excuse. 
We broke up in August because of that. He regrets it a lot.
One month later we come back together. In August he fucked like... 4 people. I stayed with one but I haven't sex with him. 
I think I trust him now. But I'm too scared, what if he do it again? 
We're thinking about living together, I'm so in love with him. 
What do you think??