It's been 12 months since my 2nd C/S, and I still can't do a situp. I can lay down and lift my legs straight up, but when i lower them slowly, there's a point where I can't feel anything and they hit the ground. Same thing if i'm sitting up and try to roll down, I just plop down, have no feeling no control at a certain point. I can do crunches, but I can only go 1/4 of the way up after that there is absolutely no feeling of muscles I can locate to go the rest of the way. any idea what is going on or why this is and what I can do about it?

big ol' bump!

It could just be a strength thing. Or it could be from the anastesia (I am assuming an epidural/spinal something that involves a needle and your back) I know that can cause nerve issues and such. have you t hought abuot seeing a chiropractor. There is one here who checks nerve stuff. Don't know too much about it but that always seems a good place to start is with a simple adjustment. Also definitely ask your Dr. about it. this may be something reletively common.

I obviously don't know all your info, but it sounds like strengh issues to me as well.
Try going to that last point before you lose it and hold there. Doesn't matter if it a "perfect" crunch or anything, just push yourself a teeny bit. Hold it a second, breathe, and then release. Do reps of that and you will build up to more!
Another one to try is the yoga "boat pose" Sit up with your knees bent, feet flat on the floor. Keep knees bent and raise feet directly in front of you. You will rock back a little on your bum, but keep your back straight, shoulders relaxed. Either raise arms straight out and reach from the shoulders or "pray" at the heart. Hold and breathe smoothly as long as you can. I noticed a huge increase in core stamina and control when I started practicing this pose daily! (You could either find a picture online or maybe someone here could add a comment to better describe the pose!!!!)