how can i tell if he likes me

I'm a cis het woman but I suspect things aren't too too different.

Normally, I would tell you to never, ever date someone at work. But I also know it can be a challenge in LGBTQ circles. So I'll give you a pass but the caveat is the same: dating at work is virtually never a good idea because if you break up (and most relationships do), then it can poison the working environment.

Be nice (without being a pest; it's a balance, you don't want to hang around all the time). Ask him to have lunch with you or go on break and get coffee. At least get a feel for being friends before anything else.

Again, I think dating is a bad idea at work. But making friends is wonderful. So hang around and be friends. And you'll start to get your answers in a far more organic fashion.