[justamom]

Toxic mold jumped to my mind as well. Then, old paint with lead
lack of sun, allergins- all can cause similar problems. You are right, so MANY things for those symptoms...

KappaKappaKitty has an excellent idea since all of you are feeling this way. Cream too is right-get checked out. A blood work up would be a good place to start.

A very simple question-have you changed your diet lately? Fruits and vegetables can have some horrid chemicals on them and if they are coming from Mexico...well, you don't want to know the details.

If you have traveled lately or drank untreated water, there is a little organism in that can really bring you down, but is easily treated.
edited-Have you checked if the pilot light is still on or that you shut off the gas completely???

I went through a similar bout and it WAS the gas heater. Could have killed us all!