When i get too hot temperature-wise. as in, when i am in a hot environment and i get hot. i get a headache and diarrhea. is that normal?

Heat stress: You're describing "heat stress", the early symptoms of heat-related illness Unchecked, heat stress can lead to heat exhaustion, heat stroke and even death. Heat stress is caused by a combination of high temperature & humidity, physical activity, certain Rx's, dehydration and impediments to dispersing heat such as heavy clothing & sports gear or excess body weight. Don't ignore these symptoms!