I had a cold since Monday, spike a 102.2 fever Thursday night, took Tylenol around the clock to control the fever, but fever always comes back after a few hours - been hanging there like this for the past three days and nights (most recent temp at 103.3). As the fever prolongs, I get short of breath and my heart rate goes up to 140s, very uncomfortable even when I am just lying and doing nothing. I'm 42 years old, ever since I turned 18, I've not had a fever this high. When I was young, I do remember very high fevers elevated my heart rate to 120s. Doctor said that was normal with the fever. But then my friend told me that this could be signs of carditis. Can someone with experience clarify what carditis feels like? How can you tell if what you're having is just the flu or some kind of complications?