Dizziness (vertigo) is another common symptom of FMS and ME/CFS. Motion sickness drugs such as Bonine (meclizine) and Dramamine (dimenhydrinate) can help control dizzy spells and keep you functional.
Vertigo is the feeling that the world is spinning around you. It's different from the lightheadedness that makes you feel like you're about to faint, or that you get upon standing.
If you frequently get light headed upon standing, it may be due to temporary low blood flow to the brain. You may want to ask your doctor about two causes of this that can overlap with FMS and ME/CFS, called neurally mediated hypotension and orthostatic intolerance.
These drugs also are antihistamines, so check with your doctor of pharmacist before combining them with other allergy medications.