I am a personal trainer certified in the TUPLER TECHNIQUE which deals exclusively with the separated abdominal muscles - called a diastises recti.
The rectus adominus (6 pack muscle) the transverse (inner most abdominal muscle) and the obliques (diagonal ab muslce) all connect at the linea alba - a piece of connective tissue from the 3" above the belly button roughly to the pubic bone. When the muscles separate, it causes the linea alba to go over the organs like saran wrap - stretching it very thin. This is the only thing separating your ORGANS from your skin - and essentially the only thing PROTECTING your ORGANS from the outside world. That is not much! When you daughter stands on your abs, she is probably literally standing right on your organs!
The woman with a larger diastisis - 3 fingerwidths or more - you can actually feel the organs - stomach, large & small intestine etc - because the muscle is no longer there holding everything in.
Your discomfort most likely stems from this - it can cause lots of problems.
You can get the book "LOSE YOUR MUMMY TUMMY" which has exercises to do to bring the muscles back together. I personally had 3 - 4 fingerwidths separation after baby #2. I completely close the separation in 5 months with the technique. An added bonus - I went from a 32 " waist to a 25" waist. The exercises are amazing, instrinsic, and very easy.
I also teach a class in the TUPLER TECHNIQUE (closing the diastisis) in Homewood-FLossmoor and Orland Park Park Districts if you are close by. Our next session starts July 31st. We also have abdominal splints we sell that approximate and protect the muscles. Corset do not work for this purpose as they come in contact with the bones of the ribs and pelvis. A splint approximates the muscles between the bones for fast results. We have physical therapists and doctors that refer clients to our class all the time. In fact, I co-teach with a physical therapist.
I hope this helps!
PS - it is common to experience back problems from a large diastisis as well. Also, it is easy to make your diastisis bigger from incorrect abdominals, another pregnancy, or any foreword forceful movements (jack knifing out of bed is the worst!) GOOD LUCK. Email with any questions!