If you have a persistently enlarged thymus gland, how likely is it that you have myasthenia gravis

HI! Just checking in... Although it appears enlarged thymus is very common in myasthenia, not sure if the association runs as strongly the other way - do most people with enlarged thymus glands have myasthenia?

Here is why I am asking... I have an enlarged thymus gland that was discovered on a CT while they were checking on something else. They have done two MRIs since and they did run a blood test for myasthenia gravis antibodies which was negative. Thymus still enlarged but not changing. Another MRI scheduled to just to check again that there have been no changes.

I did not worry too much about the enlargement and myasthenia originally as I did not have many muscle weakness symptoms - just some jaw fatigue with chewy food, some weakness in holding arms up or over head, tired on climbing stairs, little bit of slurred speech when very fatigued.

However speech has started to deteriorate over last month and its accelerating. It started one night when tired and then came back the next afternoon, then a few days later, then a bit longer, now almost every day....

Also vision weakened a lot this year - distance, not reading - but its blurring not double. Have had contacts since I was 20 but thought distance got better not worse - maybe just old on that one - ha! (in early forties).

Should I go back for another antibody test, ask for any other testing?

Thx for any help you can provide :-)