Im a merchant mariner and i might have myasthenia gravis...should i quit my career due to my safety and when could i go back?

MG...: ...Causes muscle weakness and rapid fatigue; many shipboard jobs would be very hazardous for a person who cannot trust their muscles to do their job. The rest would depend on the severity and the response to treatment.

Myesthenia: You are young, you probably need more tests to confirm the diagnosis and decide on a treatment strategy. You will need imaging of your thymus, it may be treatable with minimal medications. It is too soon to give you advice on quitting your career, more information is needed.

Should not: "might have" is not good enough. Diagnosis is straight-forward - ask your neurologist. Not advisable to consider career changes based on medical hunches. If in doubt, come ashore and have yourself fully examined in an academic medical center on the continent. Even if they were to confirm myasthenia there are treatments e.g. Thymectomy which return you to full function, if that is your goal.