Hello and I hope I can help you today. It is good that you had an MRI and an evaluation that ruled out anything dangerous causing your headaches. I also assume they evaluated your blood pressure, as preeclampsia- a dangerous complication of pregnancy that causes high blood pressure- can cause headaches and visual disturbances. Also anemia can cause these symptoms, so your blood count should be evaluated if they didn t check it with your glucose test. If you had your blood pressure tested and it was normal, it is possible that you just are not eating or drinking enough water during the day. You need to eat small frequent meals to maintain a normal blood sugar, and dehydration can make you feel hot and dizzy. Make sure you carry water with you at all times, and drink at least 3-4 liters a day especially if you are sweating. Caffeine in small doses can also help headaches and is not dangerous for the pregnancy. I hope this advice was helpful and that I answered your question. Best wishes and I hope you feel better, Dr. Brown