It sounds like the pain your experiencing is worse than any I've had - I too am currently pregnant with my third and have lots of abdominal scar tissue. So, I would definitely ask your doctor about it. But, your nurse friends are hitting the issue correctly.
When you have abdominal surgery they have to cut through several layers of tissue and muscle and scar tissue builds up and when the growing baby forces that scar tissue to stretch and move it is painful. I've had two C-sections and lots of scar tissue from taking insulin shots and when I was around 14 weeks (I'm 17 weeks now) I nearly scratched parts of my skin raw because it itched more than was painful.
It is natural to get bigger faster with each pregnancy but I'm sure the surgery affected your muscles some and that could be why you feel bigger too. I wonder if a belly support band might help relieve some of you pain? You might want to ask the doctor about that too.
Good Luck and I hope you feel better soon, I don't have any good remedy ideas because like I said, your pain is worse than what I've had - which makes me worry about how your healed from the surgery too. But, then again, all of my scar tissue is lower abdomin (below my belly button), nothing is near my belly button or above it and for me those areas are far more sensitive (which is why I don't take any shots there) so that might be part of it too. Sorry, this probably isn't very helpful but I do hope your doctor has some insight for you and that you do feel better soon.