I don't know why i never said anything

During my childhood years at a very young age maybe 5 or 6 i can't really remember exactly how old i was i just remember my older brother pulled me into the bathroom and tried to have sex with me..but he couldn't i pushed him off. It didn't just end there. My parents did drink alot so they slept most the day. I don't know how to stick up for myself and still to this day i don't. Thinking about it makes me want to cry and no he didn't actually do the sexual intercourse but i think i am messed up in my head from this and I allowed guys to take advantage of me, as i was older about 17,18. I do have a boyfriend and he knows nothing about this but most of the time i don't enjoy sex i feel really dirty like a whore, we have been together for four years. I am so crazy i always think my bf has a thing for every girl in the world. I know this is not normal but i need some advise???Please Help! I'm 25.