There was this guy who I fell in love with once, and a part of me still loves him still. Unrequited love, its such a sad feeling. Thing is, he flirted with me as well. It really makes the entire situation confusing. One day I decided to end it. This was a guy who I admired, who I looked up to like a brother and thought of as a very good friend, unsure of how he may of felt for me. It's been almost five years since it ended and from time to time I still regret pushing him away. I regret losing a friend because he didn't feel for me how I felt for him. So honestly you have to know if you can live without him as a friend before doing anything like that, and let me tell you, in the long run, it's usually never worth it to lose a friend because of love.
There is no right way to do things in this situation. Whether you stay or go, either decision will leave you with pain.
Fact is, he may not be able to help is flirting with you. I myself am possibly one of the most flirtatious people on earth, I flirt with people who don't interest me in the least sexually. I don't know why I do it, why I give bedroom eyes to people I'd never actually sleep with, but I just do. Flirting is something that most everyone does outside of relationships, if we didn't, we'd be really ->-bleeped-<-ing miserable, especially us bisexuals who's sex drives are normally much higher, at least going by the little information there is on us.
I had a friend who was in love with me, but had no intentions of returning those feelings, unfortunately I couldn't help that I was still a flirt. That I still wanted to spend time with her and buy her dinner, treat her to a movie and such. Some people are just like that. It doesn't mean he'll ever be unfaithful. Honestly you may just have to find a way past all the flirting because when you build a relationship with flirtatious undertones - usually from repressed sexual tension, or curiosity, that's the way it is going to stay. It's very hard to change the way a friendship functions. The way he flirts with you has probably become a bad habit he can't quit. If he truthfully is sexually attracted to you, it would be even harder if he's an openly flirtatious person.
I'm sorry you got to go through a ->-bleeped-<-ty experience like this. Have you two tried having a strictly serious conversation about it. Explaining everything you have explained to us? I know that he knows, but does he know to what extent of love you feel for him? Perhaps he just doesn't know how to react to it, or how serious the feeling may be. Maybe he's never felt unrequited love. However this may be one of those things that even talking can't fix. It's more like a love the relationship the way it is, or leave it. It's one of the hardest things to change since in a relationship - including friendships, there's more than just one person involved.