You're not alone in feeling this way. When you make that step into socialising with other gay people for the first time, it can be very nerve-wrecking. You may not normally be so shy, but being thrown into situations like that can make you feel that way.
When I first started going to gay bars, myself and my best friend would stand at the end of the bar, knocking our pints back and looking around nervously. We'd get drunk and have our own fun, but it was never a roaring success and we had better nights out with our straight mates. This went on for about a summer, until eventually we became more comfortable (and less drunk) and started to make conversations with other people, or engaged with people who approached us.
Joining your lgbtq soc at college will be a big help. You don't necessarily have to make a beeline for the other lesbians there in an effort to form friendships. I found that as I had always been more inclined to friendships with guys, that I socialised a lot with gay guys for the first few months, and they introduced me to other gay girls. I'm not going to say it's easy to become immediate friends with other lesbians.. in a nightclub, people are there on the pull and that's mostly it. Another piece of advice that I'm sure I could have benefitted from 7 years ago is.. if you feel like you could be really good friends with somebody, try not to ever let it go further than that just for the sake of one night of fun. Of all my closest lesbian mates, I've never been with any of them. That may not sound like a big deal, but the scene can get quite incestuous and I find my closest friendships are those with no sexual history or the drama that went with it.
I hope you find your feet and start to become more comfortable when you're out.