Indomethacin (e.g. Indocap SR) is the drug of choice in ankylosing spondylosis. I am a bit surprised that you have been prescribed two globally banned dangerous drugs: nimesulide and valdecoxib. Nimesulide is not allowed to be sold in advanced countries like US, Britian, Canada, Australia, Japan etc. Valdecoxib has been banned for causing heart problems.
Recurrence of the signs and symptoms of Ankylosing spondylosis are quite common. There is no particular reason; it is part of the disease pattern.
The best course of action for you is to take indomethacin again.
Methylcobalamin (Neurokind) has no role in the treatment of ankylosing spondylosis. This product does not appear on the international databank of quality brands. Besides it can cause unpleasant side effects such as loss of appetite, nausea, rash, diarrhoea, headache, sweating and hot sensation.