I have a very similar problem and have had it for awhile. I started tracking it and noticed the bump tends to appear a week or two before my period starts and does not go away until after my period. If I pop it, it leaves a black mark and like it said it does not hurt it just itches. Im coming to the conclusion that its possibly a hormonal thing. Some people have acne breakouts, some get fever blisters, we get a vagina bump. Thats my option but If it ever got worse, I would advise you to see the doctor.
well since you have had sex without a condom, it could be an std, it could be just an allergic reaction, it could be a pimple, or it could be an ingrown hair.
if your old enough to have sex.....your old enough to take care of you body and go to the gyn and get an exam as well as tested