Don't know if viral could effect it, but I doubt it. Are you on synthroid or anything?? If not, it still maybe your thyroid, it shouldn't flucuate like that.
If you're on synthroid and that's why your levels dropped and still no relief, you may need to switch to armour or cytomel because they work on the T3. My TSH went from 8.97 down to 1.02 with no reduction in symptoms or relief. My T3 is low....I'm going to have to look up ranges again on T3, but I'm more curious about your TSH flucuation.