I feel lightheaded and my vision is really blurry. What COULD be wrong?

I woke up one morning feeling really lightheaded and and a my vision has been effected as well. It's hard for me to describe what I am feeling but it almost feels like I am going to faint but the feeling hasn't gone away for almost 4 days.

I went to the Dr.s and they can't understnad what is going on. I am about to get a tooth removed and I think the infection might have gotten up in my gum area, but neither a dentist or Dr. understand how that could be possible sinc ei show no other signs of the other symptoms.

Can someone please give me some sort of idea what I could be suffering from as the Dr. has no clue.

I am going for an MRI next week.