I have an under active thyroid and have managed it medication. I am also menopausal haven't had a cycle in exactly a year. Recently started working again in a manufacturing environment. This week I had an episode of palpatations for 20 minutes..went away then yesterday I started to spot with light colored blood. Last night I had episodes of diarrhea. This morning I woke to a headache and nausea and mild stuffiness and sinus pressure. Could this be the flu? Or something major? No chest pain at all.