Why do I have headaches constantly all the time?

More History. I check your history page and it is blank. Are you male, female? How old are you? Do you have any medical problems? Do you have any other symptoms? When was your last physical exam? How long have the symptoms been occurring? What makes it better or worse? Have you been in an accident? Are you pregnant? Have you had a stroke? Do you take any medications? List them. Then I might have enough info.
Look in your neck. Most (85%) of all headaches come from the neck. If you have neck pain, arthritis or other degenerative problems there, it can be the cause of frequent or chronic daily headaches. You do still have to make sure you don't have sinus issues or anything neurologic going on, so get evaluated by your doctor.