Sometimes when you have a virus it will effect your teeth. Viruses travel nerves especially in your head.
I am going throught that right now. I find that gargling some Listerine 2 or 3 times a day really helps. It's called severe pregnancy gingivitis.
That definitely isn't fun. When my teeth get sensitive I use act restoring mouthwash. In a day, maybe up to 3, the sensitivity is completely gone for me. I use it early on when I feel any sensitivity.
If you're having citrus, acidic foods, drinks, etc also wait about 30 mins to an hour before brushing so your enamel has some time to harden again, otherwise your brushing away your enamel too.
Hope that helps you