Sicknesses after P.E.

Hi so recently, I have been getting very sick after/during my pe classes. I feel nauseas and dizzy. I know that people feel nauseous after intense working out, but I was only running/walking, not intense at all. On days where I have pe, I feel sick the entire day. I feel as if I am going to faint in math class (after pe). I drank water, and took deep breathes. Today, we had more physical activity than usual, and my sickness led to a fever. I pee very often to the point where my friends/family are concerned. Sometimes (not that often) I will have to pee every 15-20 minutes, but that hasn’t happend for a while. I am very tired, but I don’t think that that is very abnormal for people my age. I had joint pain today, but it didn’t hit me until my 6/7th period. I felt nauseas but I never end up throwing up. I run to the bathroom, but the second I am there it goes away. In the past, my family was concerned about my frequency of peeing, so I took a test for diabetes, which I did not end up having. That was more than 3 years ago. But than I thought maybe I just coincidentally got the a fever just today. I have felt sick in past P.E. classes, just never leading to a fever. Today I did have a lot more physical activity (an extra period consisting of running and walking). Am I just over reacting? If not, what do you think might be causeing it? Do u think that my fever was just coincidental? Should I get tested again? (If so for what). This is causing me to be very worried, so please comment! Thank you.💕❤️