My mom has sex with my friends

suspected my friend (18) might have been doing stuff with my mom (43) behind my back after I noticed some weird behavior. One time he was over at our house, I caught my mom playfully rubbing his cock through his pants for a couple seconds and another time when she was bent over getting something from the bottom shelf of the fridge he was playfully grinding his cock on her ass when they thought I wasn't looking. she has an interesting adult website 'xsofiax dot com'. So the next time I had my friend over I decided to pretend I was going to the store and sneak back in to see if they tried anything. My mom asked me how long I'd take and I told her about 30 minutes. I drove the car and parked it nearby and quickly walked back home, this took me about 5 minutes, I quietly opened the door to make sure they didn't hear me come in. I could hear moaning coming from upstairs. I slowly and quietly walked upstairs, the door to my mom's room was open and there they were, on her bed, missionary style, half under the covers. His pants and boxers were thrown on the side of the bed along with my mom's shorts and panties.I was full of different emotions, I was angry, jealous, but also really turned on. I thought it was hot my mom was under the covers having steamy sex with someone less than half her age and that my friend was so lucky he was getting to fuck such a hot MILF. I was right outside my mom's room listening to them and occasionally peeking to watch. My friend was alternating between fucking her slowly and quickly, my mom moaned quietly but consistently while he slowly moved his hips back and forth bringing his cock in and out of her. When he switched to fucking her fast she moaned hard and leaned her head back into the pillow, I even saw her wrap her legs around him bringing his young cock deeper inside of her. My mom's pussy must have gotten really wet and juicy because when my friend fucked her fast I could hear how wet she was from outside the room (later I checked her bed and there was even a stain left from her pussy juice). When he switched back to fucking her slowly I could hear them making out while he was still going at her pussy. I heard them wet kissing a lot and saw my friend kissing mom's neck and sucking on her big breasts. It actually made me really jealous that my friend was kissing and being so sensual with my mom behind my back, I wanted to interrupt and stop them, but I was too embarrassed. I didn't want them to know that I caught them so I quietly went downstairs again and loudly closed the door so they heard and knew I was back. As soon as I did that I heard shuffling upstairs, I could hear my friend quickly getting off my mom and running to the bathroom. I walked upstairs to tell them I was back and saw my mom sitting up in her bed holding her phone pretending to be texting, she was all flustered and red, she was even a bit sweaty from the sex. She had slipped her shorts back on but her panties were still on the ground when I reached her room. She greeted me by saying something like "Hi honey, how are you?" I responded with "I'm fine, is everything ok?" because she looked flustered. She said "Yeah, I'm fine, just feel a little bit sick" then I asked her "Where's (my friend's name)?" she said "Oh, I think he's in the bathroom" She got up and walked into the hallway, I even saw some pussy juicy running down her leg while she walked by because she didn't have a chance to clean up. When my friend came out of the bathroom he had a stain where his dick was because it was still covered in my mom's pussy juice (I guess she creams a lot).