Please know I am not disputing that you are sick, I believe everything that you say as what you describe is what my cousin did as well....until after 13 years we finally realized he was misdiagnosed and really had Lyme Babesia, bartonella, cpn, and mycoplasma pn.
What I am saying is the testing for Lyme and all these infections are extremely inaccurate, they miss 60%. So, you should not feel at ease after testing even if you test negative. Instead you should treat with antibiotics like minocycline which is used for both MS and Lyme. Ask your neurologist for minocycline and see his reaction, but explain it is used for both. Then, it is common for you to get worse before getting better after starting the antibiotic. You need to really become educated on your own about these infections and the politics behind the controversy.
So to recap, often it is the clinical response to the antibiotic that confirms the infection the testing is not reliable, so you should not feel at ease even with testing. Lyme disease mimics MS, in my opinion your neurologist has broken the hippocratic oath DO NO HARM by treating you with steroids before treating with antibiotics for lyme, let alone even testing you first.