What Causes The Dryness And Swell In Labia Minora?

The right side of my labia minora is swollen. It doesn't burn or itch, I'm just really dry. I was wondering if wearing a thong could cause this because I've never really worn them before and it's a little ironic that both times this has occurred I've worn a thong and its been the day after I did laundry. The first time it happened was last month. I thought I had a yeast infection and treated myself for that because the first time I experienced this I had extreme itch and vaginal discomfort I'm getting fed up with this, what could be going on with me? I'm 18, a freshman in college and I've only been with 2 guys. I was checked a few months before I got with my current boyfriend(so did he),and came back clear across the board.