it was not easy for him, you need to understand that. he trusts you tons, otherwise he would have never told you this. imagine all the shame and guilt that abusers put into the kids when they abuse them. lots of them never talk for lifetime.
men have more difficulites to say this than us women. strong guys and other stupid blablabla makes them quiet.
its good that you know. i only found out when my daughter came and told me her dad abused her. his mother and several others had abused him for many years in his childhood and it totally twisted his mind. yesterday he got his court sentence for it.
good luck to you and make sure he can trust you by being honest at all times. he has started now being honest, appreciate it!
everything is always okay in the end, if it's not, then it's not the end