To start with, sex shouldn’t hurt, and if it does, a good tip is to say “stop”, no matter what! The aftermath of sex also shouldn’t hurt – whether it’s two minutes, two hours or two days later.
Even very vigorous intercourse where there’s lots of friction should not actually hurt. It can happen if there’s not enough natural (or artificial) lubrication or if there’s some muscle tension in the vagina. Both of these can be signs of not being fully aroused (turned on) beforehand or during sex, or being a bit anxious about having sex.
A new partner or relationship can bring some anxiety for each person. It can affect the way a woman’s body (or a man’s) gets aroused and how comfortable sex feels. Good communication with your partner about what feels good is really helpful.
If you have background worry about sexually transmitted infections (STIs) or pregnancy, that can definitely affect enjoyment of sex. Getting armed with knowledge and equipment to prevent any unwanted consequences of sex should be a routine part of getting into a relationship for both parties.
The cause of your pain also depends on where it is – is it at the opening of the vagina, or other parts of the vulva? Is it related to peeing, and is it always in the same place?