Meant to add - mine was in a different spot. Also, if yours grows or gets painful it could be an abscess in which case you'd need the antibiotics asap. But a quick Dr check up never hurts. I would have had my Dr check but she has been away and since I wasn't in pain I wasn't too worried. After a hot shower last night I tried squeezing it again (as I had many times before with no luck) & finally, this time, I managed to drain it of a lot of puss (gross lol). Not sure if the hot shower helped or if it was just ready since I'd had it for months. Weird. :)
I've had similar and it was there for months (until last night). Similar age and situation to you.
I never ended up getting it checked by a Dr as it was never painful. But if yours gets painful please see a Dr so you can get antibiotics.
I've just been reading this, which sounded possibly similar to mine - a Bartholin's cyst.
Not sure if it will let me post a url to the page I was just reading or not here: http://patient.info/health/bartholins-cyst-and-abscess
I HTH. :)