Help? please??

I am 17 and my girlfriend is 16.we have sex like 2 or 3 times a day.but for a few days she says it really hurts but only for a few seconds??.and then her back wil start to hurt..any advice..should it hurt her.

Sex should not hurt but if you are doing it often (like 3 times a day) you might get a bit irritated. Try taking a break for a day or two, make sure she is always "wet" before penetration (foreplay, foreplay, foreplay)and change positions so you aren't always putting pressure on the same muscles. If the pain continues or worsens then she might want to see a doctor.

you betta stop fuckin her something can be wrong with her insides or something and you might be doin it to hard for her