I (F27) cheated on my partner (M27) with my brother (M19) on national sister day

For context, he’s a close friend I’ve had for about a year now, and he’s always called me ‘big sis’ and I’ve always called him ‘little bro’.

We’re close, and it’s lowkey sometimes been a little too close for comfort, but I always rationalized that was just in my head because I’ve never been this close to a sibling before.

We do things like call every day, say I love you, cuddle, and it’s just a cute time of usually playing video games or watching youtube together so yeah idk to me this just is so sudden and weird.

Either way from the beginning of our friendship we were siblings, there was never anything else or a hint of anything otherwise I wouldn’t have kept in contact. He’s even made a big deal telling me he wishes he was my son, or that I’m the best big sister or mother anyone could ask for.. and what I feel for him is definitely big sisterly and really maternal.

Anyway to the point.. I got really drunk (my brother was 100% sober) this last friday and sunday, and according to him we were having our usual gaming night and then had phone/facetime sex both those days.. I can only vaguely remember it but it’s had me feeling pretty sick since this is someone I’ve been calling my brother for about a year.. and meanwhile I have a LDR boyfriend of 2+ years I’m am incredibly scared to tell.. my brother keeps saying not to say anything to anyone though but he’s never even liked my boyfriend so I just don’t know.

I did ask him how things were initiated and apparently I came onto him the 1st time and he did the 2nd. I also asked why he didn’t stop me or try to but he just said he can’t deny me anything, and he’d let it happen again if it ever does.

I got kinda mad about that but I understand it’s my responsibility to be the bigger adult.. anyway though there’s absolutely no romantic feelings here so I just feel troubled about why either of us would do that or why he would be okay with that.

Now I’m scared to drink again and my brother keeps making sweet home alabama jokes and calling me mommy and I don’t know what to do so I’ve just been awkwardly laughing along… I know I messed up everything with everyone here and it’s eating me alive and the jokes are not helping me think. I just needed to get this off my head… ugh I’m lost on what to do.

I’m stressed because I KNOW things have changed now and forever, because now I have a secret, because now I’m a cheater, because I feel like I took advantage of my brother.. I feel so bad for everything.