People often need a period of adjustment to get used to a new lens prescription, and that includes glasses that correct astigmatism.
If you have just been diagnosed with moderate or severe astigmatism, or if you had a significant change in your astigmatism prescription, you may feel dizzy or get headaches for a few days while your eyes adjust to corrective lenses.
If it’s been more than a few days, your eyeglasses prescription may be incorrect, or your lenses might not have been made properly. Schedule another visit with your eye doctor to double check that your prescription is accurate.