I am an 18-year-old gay male, and I recently began to work out with my father at home because of the shutdown of gyms nationwide. He knows that I'm gay and is very accepting.
We work out alone with no one around, so we usually strip down to our underwear or just go full nude because it gets very hot in our house. It's nothing sexual. In fact, we frequently used to go to the gym/pool together, so locker rooms and showers packed with nude men (including ourselves) is no unfamiliar sight.
However, recently, he's been acting weird when I take my clothes off in front of him. He abruptly looks away from me every time I so much as take off my shirt, and he almost acts as if seeing my body is a crime. Both of us have always been pretty muscular guys, and seeing each other (even naked) is non-sexual and has been happening for years.
This especially occurs when I take my pants and/or underwear off. He acts like seeing so much as the bulge in my underwear or my dick in general is punishable by death. He sees my waistband going down, and he runs into the other room to avoid me altogether.
A joke that used to run between us is that my penis is much bigger than his. Any time that he would see me in my underwear or naked after puberty ended (around age 15 for me), he would joke that I was stuffing my pants to make it bigger, that I "stole his inches when I was born," or the forever hilarious "your penis goes in your underwear not your arm." It was genuinely funny, and both of us enjoyed that we were comfortable with these jokes and that it wasn't an awkward or sexual thing.
I also enjoyed the fact that he was proud of my orientation and my body. Now, it's almost as if everything went out the window. Working out used to be a very amusing thing for us to do, but now it's just a game of who can be the most awkward.
We also go by the rule that private nudity is only weird if you make it weird, and it still applied when I came out to him. Now, I almost don't want to show my body or face to him at all, or even talk about my orientation.
Please help me and give me some advice on how to make our relationship comfortable again. I love my father a lot, and I don't want our fun activities or inside jokes together to be soiled by the false notion that they are sexual.