Could be a ruptured cists i get them and it hurts to sit down and when you use the restroom.
I would call your doctor to ask, but I'm sure it's normal and your uterus still growing
Are you sure it is pain or is it light cramping? How long does it last? Where are the pains? Persistent/longlasting sharp pains should not be ignored. Have a word about relief options with your doctor.