I think I just got molested

I don’t know who to turn to for this, I don’t even know what to think right now. I just need to hear that I’m not crazy and that it was weird. My (19f) younger brother (13m) and I were playing headbandz on the couch and we were joking around and laughing and stuff. I had been guessing my turns very quickly and when I would win he would playfully hit me in the stomach. This time I won very quickly and he was laughing and acting shocked saying I cheated but he throws himself at me and gets on top of me pretending to hit me kind of hard when all of a sudden I feel him grabbing my nipple. Then I try to push him off but I feel him getting me from behind and I see him visibly grabbing both my breasts with his hands and that image won’t get out of my head. At that point I wasn’t pretending to tell him to get off, I really meant it, but he won’t let go. He finally does and I’m still in shock so I try to keep my cool. All these other moments this past year when he’s pretending to grab my arm or pinch me but goes straight to my chest come flooding to my head. In those little moments I always make excuses like oh maybe it was an accident or something like that. But this time I saw it happen for way longer than an accident and it really didn’t feel like it. I feel really weird and really grossed out. I don’t know how to feel. He’s my younger brother and I had a hand in raising him even when I was a child myself. But since that happened it feels so weird and I can’t even look at him right now. My boyfriend told me I have to tell someone, I don’t want to tell anyone, especially not my mom because it would break her heart to know what he did, he’s still young and I don’t want that image stuck in my moms head for the rest of her life too. Idk what to feel right now. This is like the sixth time I’ve been sexually assaulted and I don’t want to keep dealing with this, especially by my brother who I cared for a lot.

Edit: hey everyone, I have no idea what a copy pasta is, I assume you guys mean I’m copying something for clout or shits and giggles. But hey I just got fucking assaulted and I didn’t lie about it, I know that’s pretty hard to believe but it happened. My brother is also taller than me and is heavier too, I’m 5’2 and he’s 5’6, which is why by some people’s logic that I will not fight him or why he was able to grab me and molest me at all.

Edit 2: I took everyone’s advice. I asked my older brother (21M) to have a talk with me to my younger brother. At first he laughed because he realized what I was talking about and got uncomfortable that I confronted him. I explained to him that what he did was wrong even and that I was his sister, that even if I wasn’t his sister he should never grab a girl there without her consent because it’s gross and incredibly wrong. My older brother at first was livid and started calling him a bunch of names, but I told him to stop (even if he deserved it) because I wasn’t trying to make him feel bad, I was trying to make him understand that he shouldn’t do that again. I think when I’m ready, I’ll get my older brother to help me tell my father. I’m glad I spoke about it, because I know now I wasn’t crazy and if I hadn’t I didn’t want him doing that behavior on other girls; at the end of the day I don’t want other girls to go through what I went through five times prior. I was 12 years old the first time I got assaulted, and I’m deeply ashamed it happened again especially by someone who I would give a kidney to. Thank you everyone who encouraged me to confront him.

Edit 3: apparently it’s my fault I got assaulted by some men in the comments so let me clarify a couple of things. I was wearing a bra. I was wearing a thick shirt. I’ve been sexually assaulted six different times by DIFFERENT MEN OF ALL AGES NOT JUST MY BROTHER SO I THINK I KNOW WHEN TO RECOGNIZE THAT IM NOT OVERTHINKING OR OVERREACTING. I’m deeply disappointed in some of the men on this subreddit. You will find an excuse to ridicule me, instead of trying to want to correct the actions of my younger brother so he turns into a better person.