swelling

i swell during sex and it is hard to continue. it happens also when i just mess around, it doesn't happen only with sex. i can't go to the doctor bc i'm still on my parents insurance and i can't let them know, if i do need to go where can i? but when i swell, somtimes it lasts for a day or two, and it is difficult to sit upright, i have to slump down. what is causing the problem?