at the start of the year when I was shaving, I came across a small blister on my outer labia, didn't hurt when I touched it or anything and went away within a few days, but yesterday I found one again...I've only had sex 5 times in my life, all protected except once, but he only put it in for about a minute then I made him put a condom on, so I'm wouldn't think it would be an STI, but am still concerned, I've only had just the two that were months apart and went away very quickly without doing anything to them, any ideas on what it could be from?