Just saw this thread while searching about post concussion syndrome and porphyria, trying to see if there are any correlations in B-12 and folate deficiencies. There are 7 different pophyrias. Urine test is only relevant in certain ones, and porphyrins may not show up in urine even if you do have it.
Attacks can be sporadic--depending on porphyria type, lasting long time then disappearing for years until being triggered by other factors. The porphyrias are rare, hard to diagnose, and in my experience and location, good luck getting a doctor to deal with it properly.
I hope you have gotten to a good diagnosis. If not and your symptoms are persistant to porphyria, see if you need to investigate further.