Vagina zits!

About a month and a half ago I noticed there were 3 pimples on the inside of my labia. And they weren't normal face pimples. They were pretty big, I could pop them and puss would come out then the next day or 2 they'd be gone (like a pimple does) but ever since then I get about 1 pimple every other week. I don't know if it's an STD or not. I've been with my current boyfriend for 3 months and we don't use condoms. He's only had 1 other partner before me (she was a virgin). Please comment if you know what it is!