One night stand

My bf had a one night stand when he went on a night out with his friends I found out and I threw him out he's now saying it made him realise how much he loves me and he's full of sorrys he was the best boyfriend before this and I was a nightmare gf always on his case I don't blame myself for what he did but it hasn't been easy living with me I'm a crank. I love him but I don't know what to do for the best my heads really a big mess do I trust he will never do it again or not? He's never cheated on anyone before but will he see it as a pass to do it again or has he genuinely realised ? We have been trying for a baby he gave up his house to move in with me Aswel not long before this happened I'm confused why would he leave his home and try for a baby then have a one night stand and ruin it all