You are taking treatment for vit
b12 deficiency.Along with this you should start diet specific for vot b12 and vit d3 deficiency.i will suggest you diet that will not increase your weight and help to get you improve. Consult me i am aturvedic doctor as well as dietician too.
Along with this get some blood test done
Thyroid function test
Vit d3 test
Cbc test
Show me the reports