I've had this problem since before even admitting to anyone i was gay. I see something in a guy that, to me, seems a sign of them being interested. In the past, being too young and trapped in my own fantasy land, its led me to go to crazy lengths to observe them, in hopes of a more personal encounter where i could find out for sure if there was a possibility of them being interested in me. The problem is, with every situation, its always been a classmate or coworker who i wasn't acquainted with and didn't even know whether they were gay or not.
Here's my current situation. There's a guy who works at the gas station right outside my work. I go there gularly to buy coffee and cigarettes, but only recently became acquainted with him. Id seen him before and found him attractive, but never really thought about him otherwise, and had never spoken to him. I went in to buy coffee one day and he asked if i was still working in the main store because he hadn't seen me there in a while. Id never really noticed him around where i worked, so i was caught off guard by the question, especially because he wasn't the cashier ringing me up and we'd literally never spoken before that. I forced the thought out of my mind, but began noticing other things when i went in. I avoided the urge to ever approach him, for anything, unless absolutely necessary(if he was the only one working for example), but he always went out of his way to approach me when i went in. Honestly, it got those wheels turning, it put me back in that state of mind where all i could think about was whether he was really interested or it was just in my head. I don't have the guts to just ask. if i was wrong, how would a straight guy feel about a gay guy asking him out? I actually tried approaching him, and he acted totally different. He was a lot calmer and nonchalant than usual. That's about the point i decided i might consider avoiding his work altogether. I feel like I've lost it again. I know how crazy i sound, i know I'm being a creep. Its like a compulsion. I don't want to be, but its so hard not to think about it. Its ridiculous of me to be so overwhelmed by someone i only know from buying cigarettes. I feel almost like its out of my control. I'll always wonder until i know for sure. How do i deal with this? How do i find out without destroying my work-reputation? Or better yet, how do you get someone out of your head that you know shouldn't be there?

I'm beating myself up enough for being this way, so please don't reply with rude comments or insults. I don't know where else to go with things like this.