Day 18 neck and shoulder pain

I am nearing the end of a probable 21 day fast, am very weak and experiencing aching pain radiating from back of neck down shoulders. Has anyone had that?

Also, my mouth taste has turned from sweet to bitter. Guess I a wondering if I should stop now. Hunger in abdomen; not in throat as mentioned in some blogs Re: stopping when hunger returns. Just checking if this is the new "normal" or..?