you might have abladder infic
This is a guess, but look up "Skene's gland" on Google. An infection in one of these would be one-sided, painful, and the pain would be right next to your vagina. Good luck.
Sounds like you are having something that really should be checked to make sure that something else female wise isnt going wrong. Don't let things go like this, it can cause serious problems later! Good luck!