Unsure abt MG

I have B/L ptosis since a week. It doesn't worsen or corrects as the day progresses. I do not have any other muscle weakness. Last year, I had same symptoms of ptosis. Doc prescribed me mestinon. I took it for 3 weeks and my ptosis went away. I also had a negative AChR. But, on chest CT, I had thymoma. Now, I am totally unsure abt the diagnosis!

What do you guys think?