Cat won’t stop pleasuring himself

My sweet 1.5 year old boy has become a teen I guess and will not stop masturbating. Before this, he had never kneaded before. I splurged on a puffy fleece blanket for my bed and was loving my purchase until he started making biscuits and clawing up the fibers so I covered it with a top sheet. That was about a month ago and since then, multiple times a day, he will start kneading intensely, purring, and quivering (thrusting?) his bum all while staring right at me. After too many minutes he kinda lowers onto my bed and leaves a little wet spot on the top sheet and I am so grossed out and want it to stop. He has even started climbing on top of me while I’m asleep and I wake up to my sweet fluffy kitten jerking off on top of me. Is there any way I can discourage this? I’m sure it feels great which is why he keeps doing it but the ejaculating has crossed a line lol and the frequency seems somewhat concerning. He was neutered a year ago, which I thought would prevent this, but also if he has no balls is that just pee?