Hi! welcome to HCM! Dizziness (lightheadedness) is often caused by a decrease in blood supply to the brain.low blood pressure may be responsible because when the blood pressure is too low, enough oxygen-rich blood is not being delivered to the brain, and its function can be affected. Low blood pressure may be a normal physiologic condition or may be a result of - dehydration (loss of water in the body) that often occurs with infections causing vomiting and diarrhea. Fever also can cause a significant amount of water loss due to increased metabolic rate and excessive sweating as the body tries to cool itself. Anemia Heat-related illnesses associated with dehydration such as heat cramps, heat exhaustion or Side effects of certain medications used to control blood pressure and heart rate. Since you are having chills and you look pale then you must get your complete blood profile done to rule out anemia and infection .surely get yourself examined and get your blood pressure checked.and take plenty of fluids. hope this will help you! take care!