Does this count as abuse. Why Is it only just affecting me.?

I think I was abused as a child. But I am not sure weather It counts as abuse or not . My older brother was under the idea that I was sleeping , I was just pretending and then he lifted up my nightgown I was five years old and licked my bum. Being five I just got up and said I was going to my room His face was a picture he mustve knew I knew. On another Occasions While he thought I was asleep he put his hands down my pyjama bottoms I cant remember much after that. This hsnt bothered me that much until recently I have told my parents and my sister, But feel as if there is not much that I can do. I dont understand why this is effecting me now after all these years, I'm torn between weather this was sexual abuse or not. He has always been very controlling in my life with everything that I do , He is in jail for another crime at the moment not relating to anything sexual And I have never felt so free. I have a boyfriend who I have been together with for 2 years and have had a normal sex life. But ever since I came out to my sister which was a few days ago , I'm feeling completley different about sex with my boyfriend Its as if this old wound has suddenly came back and it does matter this time. I dont even know what I'm doing asking on this stupid website Probably get bombarded with loads of piss takers Its just my last place answers I cant talk to anyone.