Welcome to HCM.
Location of placenta cannot cause pain, but if there is retroplacental bleeding, that may cause pain.
Pain could be due to build up of bowel gas as a result of constipation
, or it could be due to many other causes.
Just because placenta is located anteriorly, that cannot be blamed for pain.
Hope you have delivered a healthy baby without any problems.
Wish you and your recently born baby best of every thing.