First thing is not to worry. You do not need the LP because it may not work for you. I had an LP done and in over 26 years, I have never been positive.
Blood work should have been the first thing to do in order to rule out Lyme. If you decide to use DMDs, I would not unless you had Lyme ruled out.
Now, as to your MRI, eons ago (1982) I was tested by the "new-fangled" Magnetic Wave machine. Contrast was not used, but lesions were clearly visible. That you have ongoing, active lesions is more important than the exact number. Often lesions might not be seen without the use of contrast- but you need not go through another MRI if your doctor can see the lesions.
You are more blessed than you might realize. Stay positive, you are going to be fine.