That's the primary reason I have issues with people resorting to video tapes and books as a first line of defense. Make the investment to take classes with a certified
personal trainer, someone who is qualified to teach Pilates (preferably beyond just Mat certification). Take the classes, private or group. A teacher could critique your movements and form and personally customize the modifications.
She could give you feedback.
A video won't do that. A video won't point out what you're doing right or wrong at that particular time. It's open entirely to your subjective interpretation of what you're seeing, or reading or hearing....and we all perceive things differently.
This is my favorite part of teaching, - demonstrating how two or three exercises which "look" identical to the outside observer watching them performed, slight changes in how you think, recruit your muscles, move, think, etc., can turn what appears to be "the same" exercise into vastly, vastly different exercises. They LOOK the same, but they do not feel the same when doing them. You cannot get that understanding without personal feedback.