Should I tell my son about me and his friend having sex? [I Relationships And Dating]

I'm a single 47 year old woman and I have an 18 year old son. My son has an extremely hot friend who is also 18. They've been best friends for years. Every time he came over we would flirt and we joke around. I really liked him a lot and he liked me too. About 3 months ago my son wasn't home but his friend stopped by and we started to talk and flirt. He told me that he had liked me for a while and he told me he wanted to have sex with me. I told him i liked him a lot and that I also really want to sleep with him but that we should wait a little before we have sex. I gave him a BJ to show him I was serious.

About a month later after we had discussed it fully and did some thinking we decided we still wanted to and we had sex in my room. We've been having safe sex the past 2 months and it's been amazing. He's so big and good and we both love doing it together. We do it about once a day for the past 2 months usually in my room or sometimes my sons room when he's not home. I know I can trust him because he hasn't told my son or anyone else.

It's perfectly legal and we're being safe so I'm not asking to be scolded. I'm starting to feel guilty. Not because he's my son's friend, but because he doesn't know. I originally didn't want him to know, but now i'm not sure. I feel bad sneaking behind his back and sleeping with his best friend. I dont know if he'll be ok with it and be mature enough to handle it or be mad at me and his friend. Either way i'm not gonna stop sleeping with his friend because we're both adults not looking for a relationship just good sex and we both love doing eachother. But no matter what I still feel bad he doesn't know. So should I tell him?