Transverse myelitis is simply an inflammation of the spinal cord, which can have various causes. To explain all of your symptoms the myelitis would have had to be very high in the spinal cord. The other possibility would have been inflammation within the brain. If the MRI's were done with contrast it would be unlikely to miss inflammation. Other conditions to be considered include connective tissue disorders, vitamin B12 and folate deficiencies, lyme disease, and syphylis to name a few. If the MRI is truely normal, perhaps an evoked potential would be useful to test the sensory pathways.
If this is transevers myelitis the majority of these cases are self limited and would not progress. Regarding herpes, the virus lives within the nerve cells and occasionally reactivates. This is why an outbreak always occurs in the same areas. However, I have never heard of herpes infecting the spinal cord.
If you do not receive answers to your condition with your current neurologist, I would encourage you to obtain a second opinion. Good luck.