I am 9 weeks post op tummy tuck with muscle repair and flank lipo. My uppermost ab muscle still hurts...a lot! is this normal?

I was told I could start working out freely however I still can't sleep on my stomach flat because it hurts so much. I tried doing a sit up and it felt like someone was stabbing me...doing a plank..yeah right! Even just stretching back (a backbend) feels like my abs are going to rip open. When I went for my 6 week post-op checkup my dr said my abs were good. So why am I STILL in so much pain?