It might also be migraines I suppose. But migraines can be caused by Celiac disease.
One person in about 130 has Celiac disease, so you might as well get tested.
I have migraines, severe migraines which induce seizures, and I have numbness primarily on the right side of my body as well as dizziness and nausea. The numbness only lasts a few minutes at a time though; however, the tingling, dizziness, and nausea can last for hours. My current headache has been going on for three weeks now with the actual migraines and other symptoms being intermittent.
Has anyone told you what your face looked like when it felt numb? Often times I cannot clearly remember what happened during the times part of my body felt numb and while I would swear the numb areas were overly relaxed I am told that they tighten up and can be rock hard. Other times I've been told they couldn't tell anything was wrong until I tried to do something - like talk - and the affected side didn't move appropriately.
I'd recommend taking a friend or family member with you to an appointment or the ER next time it happens. One who has seen several episodes if possible so they can give their view of what happens. You have no idea how many times I've felt like I remembered everything and could tell you second for second what happened and it turns out I missed a chunk of time or I felt one way and another thing happened. Comparing the two stories can really help.