Hmmmm, it is a very tricky situation. I always think you should trust your gut feeling. I mean, unless you're particularly deluded or have a far to high an opinion of yourself (neither of which applies to you I should think)you're not going to just think they might like you for no reason surely?
Although, I've sometimes thought male friends fancied me and after a while have decided that they didn't at all, but these are only vague and brief feelings on my part (probably coming when I'm being particularly self loving!), if I really felt, over a periond of time lasting more than about a month that one of them may fancy me I would probably trust my intincts.
Actually, that's easy to preach but the truth is I've never really believed anyone but my boyfriend has fancied me but surely the law of averages suggests at least one more person must have?! So, in conclusion, I just don't know I'm afraid. Sorry!