Body pain muscle pain comes and goes.

I get joint pain and muscle pain that comes and goes every month I don't have any idea on what's happening to my body I was diagnosed with B12 defiency back in 2018 and was given nirvegen plus injection and my b12 level was back on track and everything was fine until now I started feeling cold hands and extremely cold arms and legs and checked my b12 again it was less but not very less So the doctor put me on this injection called optinueron for 7days everyday and then once a week for a month and then once a month for a year and even after taking the injection (optinueron) my symptoms didn't come down We did couples of blood test everything was  showing normal. But then my muscle pain keeps coming and going once a month but recently I started having the pain occurring 2 times in a month my muscles in my legs arms and neck and my joint hurts so bad I don't know what's happening Someone please help