Fallen for gay best friend

He knows im interested in men and that I've never actually been with a man. We work really well together and are as close as friends can be. We even lived together for a time. He is supposedly done with his toxic boyfriend and my girlfriend left recently. I've fallen for him surprisingly hard (had crush on him for years) and these new feeling are far superior to my old feelings. It feels gut wrenching not to say anything But I'm scared to lose one of my last friends especially since I just moved to a new city. What should I do?