Hello Mimi, when i was using Tramadol [ ultram same thing] but i noticed after a while, i built up a tolerance for that med, i was on 2 x 300 mg slow release Tramadol daily, seeing i couldn't take any of the other strong meds the only way
i found relief was if i backed off to 200 mg twice a day for about a week, put up with it all

, then went back up to the 300 mg it worked again for me every time.
I also took Endep 150 mg at night and 25 mg in the mornings, that helped the burning.
With b12 supplementation, its best to take a good quality multi B every day as well, as the b12 needs the other B vitamins to make it work better, and if your taking the best form of b12 [methylcobalamin] it is best to take it separately on an empty stomache, for better absorption.
Just remembered, i know one guy that couldn't get any relief from the typical drugs for PN, but has found great relief using the fentanyl patch.
I really hope you can find some relief, best wishes