Would a headache caused by a brain tumor feel like it's on the surface of the head? top left of the head, mostly when bending over, but not everytime

Parietal or temporal: Headache can be related to a TMJ dysfunction and sometimes the origin maybe coming from the occipital muscle. If a person is in a lot of stress, contraction of the muscle in a deranged side of the jaw can trigger a headache. See your M.D. Who can refer you to a neurologist and if your blood test, exams, and other diagnostic procedures came out (-), see a TMJ doctor.

Please don't worry: Thankfully your history does not suggest a brain tumor. The human brain has no pain sensitive structures and thus brain tumors present more commonly with other neurologic symptoms or seizures. You should have a neurologic evaluation to set your mind at ease. Good luck and get well soon.