I think he is not ready yet for the serious relationship.
Some guys just want to try new things but they might not see how important the relationship is to you. I don't understand how he could do that if he really cared for you. So I think he lied to you. We should chat some time about the matter.
I don't think the female population knows why men do what they do. Okay I think that you should yeah let him earn your trust back but if he screws up again then you should forget about him and move on.