Irrationally Uncomfortable?

Sorry for the novel, but I had to give some back story....

Okay first let me preface by saying that I am trying to be objective about my feelings, explore them more, and try to figure out why I’m feeling them in the first place, so I’m not here to rant or belittle anyone, I’m just hoping that maybe other people’s opinions will help me better understand my own and ultimately get over my issues. So, here we go...

I met my husband 4 1/2 years ago and we’ve been married almost 2. He is an amazing person, so sweet and caring, and intelligent too. We get along really well (he’s my best friend), but if I had to say there was any area of improvement in our relationship, it would be sex. I’m a very sexual person, he’s not. We’ve gotten better at learning each other’s bedroom languages, but it’s still not my favorite subject, whereas it once was in other relationships. Idk why that’s relevant, but it feels like it is.

So before I met him, he participated in Karate and kickboxing, and was really good from what I’ve heard from past teammates and coaches. He hadn’t been in the sport (for personal reasons- his coach wanted him to go semi pro in kickboxing but he didn’t want to leave his family), for about two years before I met him. Since we’ve been together, he’s dabbled in Brazilian Jiu Jitsu on-and-off, and I’ve gone to some of his practices. I never really enjoyed it much, but I actually did try to work out with them once (it’s co-ed) to show my support. It wasn’t my thing and he was fine with that.

Recently, about a month ago, he’s started going back to BJJ at full force. Twice a week, for two hours a day, and it’s all he talks about. I come home and he’s watching videos on rolling, he’s showing me different things he’s learned and wants to do. I’m so happy for him that he’s found a passion point and is becoming healthier, but there’s a weird feeling I have about it all. Keep in mind, I 100% recognize that this is MY issue, that it’s (so far as I can tell) irrational, and I’m probably being ridiculous, but I just want someone to explain why I’m having these thoughts in the first place...

There’s something about this sport that just makes me feel really uncomfortable. Idk how to explain it without coming off as homophobic or jealous (which I absolutely am not- I myself identify as bisexual, but have chosen to be in a heterosexual, monogamous marriage because I fell in love with a man, it’s cool), but something about imagining/seeing him literally crawling around on top of other sweaty people, wearing essentially a robe and spandex underwear, makes me cringe. I can’t figure out if it’s because the types of moves they do seem sexual to me (I used to be quite adventurous/agressive in the bedroom, so being under someone who has me pinned down with their nether regions touching mine seems pretty damned intimate to me), or because especially seeing him that way with other men, knowing he is completely heterosexual, feels “off”...

I don’t want to say anything to him because I want to be supportive, but with how obsessed he’s getting with it, I know it’s going to be even more in my face than it is, and idk how to process that. Any advice would be welcomed.

TL/DR: my husband is in BJJ and it makes me feel weird