Hi Cindy, no need to be worried! There are many different kinds of astigmatism. Sometimes it just manifest as a little blurriness. The kind I have is similar to this Wikipedia description. "Astigmatism ...in some cases vertical lines and objects such as walls may appear to the patient to be leaning over like the Tower of Pisa."
In my case I tend to pull things up and to the right with my vision, as though the image was printed on a cloth and somebody gently pulled up a little on the top right hand corner. Looking at the the work of El Greco, makes me suspect he had a similar type of astigmatism!
I recently discovered a great new way to correct for this problem. I take a digital photo of my work, open it in photoshop, and then I flip the piece horizontally. Augh! Flaws leap out like beacons. I don't know why, but it is even better than using a mirror. I use the mirror while working but at the end of a session, or after a few days, before I move on to another stage of the work, I do the photo-flip check. Fresh eyes, as Tom Edgerton put it!