I tried to have sex and it was so excruciatingly painful and stuck his penis in but i don't know if he got far and i've been bleeding all day??

Postcoital bleed: May be trauma or could have hit your cervix. Does need an examination to check for some rarer conditions related to your cervix so will need to see doctor. Sometimes using lubricant or changing positions can be helpful

First time?: This is to be expected, if it is not there might have been other trauma. If it is continues or is heavy bleeding please see your doctor.

Vaginal tear: Tears in the wall of the vagina can happen from time to time, especially if there is a size mis-match between partners or sexual activity is particularly vigorous or there is not enough lubrication. You may be able to see the tear if you self examine with a mirror. If it has settled &/or you can see a tear it is probably safe to watch and wait. If not or you are still bleeding then see a Dr.