I can't tell when others are attracted to me, and it upsets me.

No matter how hard I try to read up on this or ask for people's help, I cannot tell when another person is attracted to me. And I feel bad about it, because what am I supposed to do if I want to do anything flirtatious or date? Trial and error? Just try it with anyone I think is attractive until I learn what the patterns are? Sounds like a quick way to be seen as That Guy. Even if I just ask, that's still a pretty forward move, letting someone know I think of them like that. So I really do not know what to do there, and it upsets me.