Does Taking B12 Injections And Ferrograde Cause Tiredness And Breathlessness?

Hi, I was recently diagnosed with B12 or Pernicious anaemia, I have regular monthly injections and take a combination tablet called ferrograde, I get really tired and breathless, is this all normal, also I questioned if I had thyroid problems as I have steadily gained a lot of weight prior to this diagnosis. but just eat a normal diet, I don't overeat but am now 16.5 stones, am really hating myself.