Should I be concerned if I have post-partum bleeding?

No. After a delivery, either c-section or vaginal birth, it is normal to bleed for up to 6 weeks. Your bleeding can also go back and forth between heavy and light and you may have different sized blood clots . If you feel like you are bleeding excessively call your doctor.
Yes please call. Your OB as ppartum bleeding should not be heavy at all and the lochia should be decreasing the farther you are from delivery.