Hi, Kimg. Welcome!
As you can see by this site, there are many mitochondrial diseases. In order for you to be properly diagnosed, they would need to do a muscle biopsy. Of course, you would need to see a neuromuscular expert first, to be fully evaluated for other diseases as well.
Do you mind my asking where you live? That may affect the experts you can find.
Some diseases, such as CPEO have a progressive eye involvement. It may progress so slowly that you might not notice your eyes are affected.
Chronic progressive external ophthalmoplegia | Genetic and Rare Diseases Information Center (GARD) – an NCATS Program
Was the medicine the doctor gave you Mestinon/Pyridostigmine Bromide? That's a typical drug for MG. Were you given any direction of how much to take and when to take it?
Try this. If you have one eyelid that is dominantly "droopy," then pull up on that eyelid for ten seconds. Watch your eyes. Does that eyelid go up and the other eyelid go down? That's called enhanced ptosis and is seen in MG.
There's another test called the Ice Pack test. You could try putting a cold washcloth on the affect eye(s) for a few minutes. Then see if that makes any drooping better. You could also take photographs before and after this test and the one above. Then compare them. Do it with the same head tilt, lighting, etc.
There are other signs of ocular MG that a neuro-ophthalmologist (not a regular eye doctor) can test for. Do you have one in your area?
That doctor is incorrect about most people having ocular MG. Most people progress (or start with) generalized MG.
Are you short of breath? Do you have swallowing issues?
The important thing now is to find an expert to fully evaluate you. In the meantime, if you can't move, breathe, or swallow well, then you need to seek out emergency care.
What else can we do to help you?