What do I do?

I know most would probably say wait and ask you doctor. But in order for me to graduate in need 3 pe credits. But when I start walking on the treadmill I get really dizzy and have these cramps that make me cry. My teachers told me to stop until my doctors appointment but I need these credits so I can be done with school by the time my baby comes....has anyone had this? If so what did your doctor say?