S.B.
STOP doing crunches now!!! The fact that you had 2 c-sections and tried doing crunches which didn't work, indicates that you probably have a diastasis recti(split abs). Crunches will only make it worse. It's very easy to test if you have this. Lie on the floor on your back with your feet flat on the floor and your knees up. Place your fingers on your belly in the midline at your navel, and just lift your head off the floor. If you feel your fingers dip between your abs in the center you have this split. I'm guessing it's a big one. I had a c-section, and also have quite a split.
The best abdominal exercise you could do for now is a plank. That is the push-up position on your elbows drawing your navel in and holding for a count of 5. Make sure to do this with good posture...head in line with spine, shoulders down and back, chest lifted, abs and glutes tight. Repeat as many times as you can, and try to do 3 sets a day. The other thing you can do is whenever you have time to rest, breathe deeply, drawing your navel in on the exhale and holding for a few counts. Also, there is a book called, "Lose your Mummy Tummy" I've forgotten the author's name, but she's an RN. I'm sure you could do a search on Amazon to find it. Good luck!