Confused...what should I do?

[Bяian ♪]

Whether your mother is right or wrong in telling you it's not a big deal she should still be listening to you and looking at all the available options to help you get over it. You also stated you wish you could go back and stop it, well come on, you were 6 years old, you didn't have a clue what was going on and why he was doing it. No-one deserves that at that age but as Omni said, teenage boys can be very dangerous with their hormones so he might well have turned into a decent human being and if you tried confronting him he might be able to tell you something that will ease the pain and help you forget, even if it's just a simple apology. Tell him how you feel, how it makes you cry and how he has ruined your love and social life. Knowing he is ashamed and apologetic could be a big step in you getting over him and moving on with your life.