What do you mean by vaginal swelling? Do you experience any pain during it? Was it injured to cause swelling? Actual swelling in the vagina is abnormal and if you have to stop sex before you orgasm because of it, it might be worth seeing a doctor about.
If you are experiencing bladder pain, you should go to the doctor like the other person advised.
Sounds like a possible UTI (urinary tract infection), which are common esp. in women. If you notice extreme pain and having more difficulty going pee, then you definitely need to call up your dr. and explain your symptoms. If you do have a UTI, they can prescribe over the counter meds. or prescribe you some antibiotics... Don't wait to call, because the pain will only get worse and it is totally treatable...
My gf often gets a water infection/cystitis after having rough sex, so definitely especially if your partner has a large penis. Drink lots of water to try and flush it out, if it doesn't go you can get drinks to clear it from the chemist or some pills from your doctor