There were times when I feel the same also. Too weak to cry, too painful to do anything (like the pain suck up my energy). But i think your case must be more severe. I realized after some pattern that whenever I feel worsen (ex:toothache worsen), I become more emotional. I tried not to press hard myself just to cry (it acquire energy even to cry!) even though crying is a release I need. This is when all the negative thoughts come across my mind (depressing, hopeless, self-blamed, etc.). But I learn to lean on God's grace each and every moment. So I tried to remind myself that all those negative thoughts are side effect of the biochemistry run in my body (it is indeed one of the symptoms of heavy metal poisoning-it messed up with your emotion, not just your physical body), it's not the real me. On the other hand, I tried to have a nutritious intake (good diet, supplements from the doctors) so when I got a bit of energy and I feel like crying, at least there are some tears can be shed (and feel release afterwards).
I think for your situation, your body now is totally depleted and exhausted, physical and emotional. I can only pray for you. Hanging there, grief whenever you feel like it, but need not to press hard your self to cry out when you don't have the energy. Eat and sleep as much as you can, once you got back a bit of energy, you can cry. Be relax about how long you feel this way. Give yourself some time. If you need to vent out, you can try other way (speaking, writing, etc.)
God be with you,