Lately i cut my perineum by sex, inside cut is white and after days there is a white head bump, so it goes away but cuting again or by itself!!

May be an infection: Small lacerations or cuts may occur after intercourse. In your case, it may have become secondarily infected, based upon how you describe it. I would clean and irrigate the area and you can even apply antibiotic ointment to the area. If it worsens or becomes red and painful then you should have your Gynecologist look at the area.