Gay friend is really weird about my relationship

For context, I’m a straight man. Been in a relationship with a woman for a few years. I’m 25. My gay male friend is 26.

Me and this guy have become close friends after being coworkers over the last few months. We hang out more outside of work. Good friendship.

However, he gets really weird whenever my relationship gets brought up. It’s not like I’m yapping 24/7 about her, but whenever she gets brought up, he goes quiet and gets annoyed or changes the topic of conversation. It makes me wonder if he’s jealous? Or into me? That sounds full of myself but I just find it strange and it makes me kind of uncomfortable since he’s a good friend, just this specific thing is weird.