I can put my nose to the floor in butterfly, my hip flexors are quite flexible, and my hamstring flexibility isn't bad (100 degrees from standing). However, when I try to do pancake, I can't even sit up without having to prop myself up. And when I do try to sit up, something in my hips cramps up and I have to stop. Can someone tell me a stretch I can do to alleviate this? It's a major roadblock for me right now.