God...its so damn easy guys. First of all, if she's with you already, that means shes got interest. If she sleeping with you, then all you have to do is not fvck up in a huge way, get overly mushy, or get boring. Show her a good time, fvck her very well, and don't be a knob. Thats all it takes...girls love being in relationships more than we do remember!!
Its not rocket science.
Pancho