I am a horrible person

Last Saturday my sister sent her kids to our moms for the night and I went out with my sister and brother in law, We were all pretty drunk when we got home I went to the spare room in the basement, I got undressed and crawled into bed, I was laying there with nothing on like I always do when I could swear I heard a noise outside my window, I got out of bed and turned off the lamp, I looked out the window and thought I could hear footsteps, I was freaked out and closed the window locking it.
I threw on a pair of shorts and a tank top and went upstairs, I went to my sisters room the door was open so I knocked softly and walked in, My brother in law and my sister were both laying there with very little covers on and my brother in laws ** was exposed.
He is a tall guy with what I would consider an average build, Not muscular but not overweight, Just nicely built, I have always had a great relationship with him and we have spent a lot of time alone, I quite often stay with him while my sister is out of town for work so there is someone at home after school or so I can watch the kids during the day while he is at work.
I have on occasion noticed the outline of his ** in pyjama pants or sweats after showering when I stay at their house and I cant say I haven't noticed that his ** is large but I have never seen it anywhere even close to hard, He was laying on his back, One arm above his head and one across his stomach and his ** rock hard.
I am only 24 but I have seen enough penises to know that he is HUGE, I was shocked to say the least, Laying on his stomach it reached just past his belly button and it is THICK, like unreal thick, I couldn't believe how big it is, Huge, veiny and the girth, Oh my god, I cant believe the girth he has, I am not making excuses but I was drunk and haven't had a boyfriend for a while and I was admittedly thinking about maybe having a "Session" before being startled and fleeing my room.
I caught myself breathing heavy and I was already **, I remember thinking "What could it hurt to just touch it", I reached down and took it between my thumb and pointer **, I stood it straight up, I remember thinking it was almost as long as my forearm, Just then it slipped out of my fingers and smacked against his stomach, I froze thinking he would wake up for sure, I stood there still staring at him but he never moved, I waited a couple seconds and touched it again, I ran my fingers along the underside to the humongous pink ** and rubbed the tip with my thumb.
I took it in my hand wrapping my fingers around it and couldn't even touch them together, I slowly stroked it and massaged his ** with the other hand, It only took a minute or so and he started breathing heavy then started moaning a bit, He puled his hips back then thrust them forward and I panicked, I knew exactly what was happening and I bent down, Wrapped my lips around his tip and then it happened, I cant believe I took it that far and I feel terrible about it now but at the moment I just wasn't thinking straight, I sucked for a couple seconds and suddenly I felt him slide his hand up my shirt and grab my **, I looked at him and he had his eyes closed but he came and I couldn't think of anything to do but keep going, I sucked until he was done then stood up.
I still had his ** in my hand and he was still hard, When I stood up he took his hand out of my shirt and cupped my ** cheek, He was rubbing me from behind and slipped one ** in the leg of my shorts, I was so ** I couldn't stop and let him slide a ** in me, His ** kept twitching and a bit more came out, I looked at him and my heart stopped, He was looking right at me, I started shaking and stepped back, he was really drunk but looked at me and slurred "MMMM, that was nice", He rolled over and threw a leg over my sister, I snuck out of the room and went to the couch, I was sitting there for about fifteen minutes before I heard my sister say "What time is it?", My brother in law said "Who cares", A few seconds later I heard my sister moan "OOOHHH god", I sat there and could hear her moaning and soon heard her "harder, harder", I was still feeling terrible but couldn't help myself, I stepped into the hallway and leaned over peeking in their door, I watched my brother in law shoving his huge ** in my sister who was face down with her ** in the air, I could see his whole ** as he slid in and out of her, She only took about three minutes and buried her face in the pillow muffling her **, He kept going and lasted a couple more minutes before saying "roll over", When she did I left the doorway but I could hear him say "** it" and then heard him moan out loud.
I went back to bed and was so nervous when I woke up that he would say something but I stayed for three hours before going home and he was totally normal toward me, Is it possible to come and not remember it, I have never been that drunk to not remember it in the morning and he looked right at me.
I have to go watch the kids next week for two days and I am so nervous, I feel terrible and don't know what I am going to do if he says anything.