Male paramedic crushing on his male emt partner who doesn't know. Need advice

So im a 27yo gay male working in EMS and im currently partnered with a 23yo male. For the life of me I cannot read him at all. I am highly attracted to him and hes very sweet so I dont want to say or do anything to mess anything up between us. We work really well together. The thing is I cannot figure out if hes straight, bi, gay or what. From time to time he will see a female and try to make it very obvious that hes interested in her or acts like hes distracted by her. This is exactly what I used to do when I was around my straight friends before I came out to them. To my knowledge he does not know im gay. Neither of us really have much stereotypical gay characteristics. I try to make some minor jokes that could be taken as gay or straight as I dont want to be too forward and hes always been a good sport about it, never seems to be offended. He has no gf and doesnt really talk much about girls or past relationships. Hes into Nsync, backstreet boys, and some other boy bands of that time period but still listens to todays music as well including Justin Bieber. This guy is one of the best partners I have had the pleasure to work with. The deal is I want him to know im gay and I want him to know im interested in him. The longer this lasts without me knowing the harder it is to work with him. I find my self thinking about him on my off days. We hang out from time to time on our off days to watch movies together but seems really shy outside of work. He recently talked to another coworker of ours that is openly gay and he asked him how he knew he was into guys. Thing is I dont know how he would react if I told him I was gay and interested in him. Im afraid this would screw up both our friendship and our professional relationship. If I tell him and hes not interested then im okay with that but I dont know how to tell him and im very afraid of how he would act around me.