Myasthenia Gravis brought on by Iron Infusion/possibly Covid

I have had an illness for over two years that no Doctor can figure out.I just went to an infectious disease doctor who tested me for alot of diseases including Myasthenia Gravis.The specific test he ran for Myasthenia Gravis came back with an antibody that was borderline,but labcorp ran additional tests and told my doctor it was negative.I have slow chewing,talking,swallowing,my breathing is not normal because of no strength in my stomach or diaphram,trouble walking,No gag reflex,extremely dry eyes that are painful,squinty and extremely sensitive to light.I have alot of other symptoms,but I thought those were many that involved in MG.I was looking at LEMS,Polymyositis,Gullian Barre and a few other diseases.I feel like they all have similarities.The problem is the Doctors are not finding much of anything with the tests they have run on me.I had a reaction 5 days after an iron infusion for anemia and by 6 months I was bedbound for months.My whole body was basically attacked.Has anyone had Myasthenia Gravis with a Borderline or negative test?I know Autoimmune Diseases are hard to figure out.I am just trying to figure it out myself with help from others.The Doctors I have met with can't help me.