Hi,
I'm a straight guy, but i thought I'd try and answer your question anyway.
I find that women (in general) can be attracted to all sorts of different types of people... it's not just about good looks (contrary to what "certain users" here think lol). Some girls may go for the pretty boy/ girl; others may go for someone dark and mysterious; others may go for a real diamond in the rough etc. For example, if you look at Liam Gallagher... I don't think anyone would say he was a particularly attractive guy (as in good looking), but look at the standard of some of his ex's (e.g. Patsy Kensit, Nicole Appleton etc.).
Admittedly, I don't know many full-on lesbian women (I know plenty of bi-girls, but that's another story)... but I do know quite a few gay guys (incidentally I don't know any bi-guys either lol). From those that are in couples, I typically notice that one tends to adopt the more masculine role while another will be more feminine. As I said, I can't even pretend to be an expert on the dynamics of lesbian attraction or relationships... but is it possible it's the same sort of thing happening here?
The other thing is if you can stand out from the crowd (for whatever reason), you'll find people will be more likely to take an interest in you (for the right or wrong reasons)... so if you were the only or one of very few "mascs" in your places of choice (I don't think I'm allowed to use the "Q" word lol), it's bound to work in your favour.
If you're attractive, then I would expect you to get a lot of attention wherever you go... but if you're getting attention from some girls, but not others, then it's more likely the type of girl you are that's attractive to them (i.e. that girl goes for the type of person you are), rather than being classically "pretty".