workout pain 15months later

My son was born via csection 15months ago, no complications from surgery and my incision has healed nicely. I am an avid runner and workout 4-5 times per week. Obviously my abs were weaker after the pregnancy but I still have lower ab pain when doing core workouts that focus on lower abs. Not the good muscle burn pain but a tightening/pulling tearing/buring type pain. Most ab workouts don't bother me at all and my upper abs are fine, like I said just the intense exercises that focus on low abs. Just wondering if anyone else has/had that, if it's normal since the muscles were seperated or if it's something I should talk to my doc about. TIA.