Nipple inferno

Rosemerry • Friends for years, now newly weds with one on the way!
Ok, so on certain days (mostly days I excercise) my nipples feel like they are on FIRE! To the point (no pun intended) where I have to take everything off that's touching them (bra/sports bra/bed sheets/vest/shirt etc.) which is impossible at work. What is this and what can I do?