I'll attempt to read between the lines here.
It looks like each time you act like one of their mates, then one of two things happens after a few weeks(?):
A) They like you but you don't like them (at least you're attractive!)
B) You like them but you're pidgeon-holed into friend already and they won't see it unless you are massively forward.
The best way out of if is to be more upfront. Men are generally emotionally dense creatures, and we don't usually "get" flirting. If I tried to pursue every woman who flirted with me I'd be overworked, therefore I assume that like me most men don't take it seriously either. You probably need more than flirty. Go for a kiss! Physical contact sends a clear message, flirting could just be playing.