5 weeks post medical abortion, ultrasound showed remaining fetal tissue. currently bleeding and cramping is it possible to pass the tissue naturally?

It's possible to expel retained products of conception naturally, but five weeks after the abortion you may need a D&C and your new pain and bleeding could be due to several other serious possibilities including infection and even a new ectopic pregnancy. You should immediately see an OB/Gyn specialist or go to the emergency department. Assuming this will take care of itself is not worth the risk.