Headaches can be caused by many things. The most common causes are stress and hormonal changes, but there can also be a neurological link. Tumors are not as common, and shouldn't be considered right off the bat, but cannot be ruled out.
If you are under a great deal of stress, daily headaches can be a common occurrence. The problem lies when you are unable to get relief from these headaches by taking Tylenol, Ibuprofen, etc. If this is the case, I suggest you contact your physician to be worked up for these headaches. You may need to take a beta-blocker, or other daily medication, to help prevent these headaches.
If they are migraine in nature, you may need to be treated for migraines. Migraines typically cause a stabbing type pain, often behind an eye, and cause you to be very sensitive to light and sound. I hope that you get the relief that you need soon, and I hope this helps. Good luck!