Search Results: flirts with me even though has a girlfriend

I don't mean dating. I mean FLIRTING.
See at my work place, there's plenty of single dudes roughly my age. And I've found myself flirting with three of them. But not dating, I want to make that clear. I've never even hung out with any of them outside of work. I did hang with one dude, but he's married, and it was like a last minute thing when we both realized we were bored as shit but didn't have work. So no romantic interest there.

But there are three guys, all of whom I would be THRILLED to go on a date with if they asked. One of them I'm POSITIVE has been flirting with me right back. Like that's not even a question, another I'm pretty sure he at least likes being flirted with, though he's kinda shy so I'm never sure if he's flirting back with me or not. Then the last guy is the one who all my bosses seem to think we have a thing for each other, because we do, but I THINK he has a girlfriend, which is why I'm flirting with the other guys, because if he DOES have a girlfriend (I'm still trying to figure it out, if he does, he does NOT talk about her, but I don't wanna like, ruin his relationship).

So I'm still pretty early on in flirting with all of them, with the exception of the dude who might have a girlfriend, but I'm trying to keep my options open in case the others don't even wanna date me. If that makes sense. But I really don't have a lot of experience in dating, so I'm not sure if this is something lots of people do, or something that's just weird and bad. But also what if one ends up being like, a drunk or something and I just don't know about it yet? I'm kind of looking for someone who can go the distance, so yeah, trying to keep my options open.

So, there's this guy whom I've been friends with for several years and when we were introduced by a friend I immediately liked him. The same friend that introduced us also told me later that he's also interested in me, but he never took the next step. Why? (The friend also told him that I had a crush on him as I discovered years later while talking to the guy) Somehow he and I lost contact several times, but every time we met the story repeated itself and when we had contact on a regular basis (finally!) he had a girlfriend all of the sudden. When she broke up with him we had even more intense contact, but he dropped me when they got back together. Nevertheless, we met quite often in the past month because we drove to work together and he kept saying things like 'it would be such a fun if we worked for the same company' and compliments me exactly like during the time he had no girlfriend (back then he almost touched my breasts 'accidentally', for instance). Why is he flirting with me for years and still has a girlfriend? Am I his number 2 even though he knows me far longer than her?