I'd say stop taking your temperature. Monitoring ALWAYS leads to an increase in anxiety. Even in this situation it happened—you took it "you don't know why," and as you kept taking it, you noticed a downward trend and all of a sudden you got concerned. If you had started taking it at all, you wouldn't now be worried about it.
In this fight against HA, we are our best and first line of defense—it's hard, but we must start helping ourselves out by putting a brake on self-sabotaging behaviors.