Why am i bleeding after sex then when i have sex again i am not bleeding?

Could be: Several things: most likely relation to period (especially if they're somewhat irregular) or very vigorous sex especially after a dry spell. Is there pain associated? Any chance you are/were pregnant? If it persists, I'd suggest you see your gyn.

Bleeding with sex: You need to be seen by your doctor. The bleeding could be caused by an infection, trauma or problem with your cervix.