Most medications do not prevent you from donating blood. Common medications such as those used to control blood pressure, birth control pills and over-the-counter medications do not affect your eligibility. If you have recently taken antibiotics, you must have completed the course prior to donating.
Yes, a tooth infection can cause a headache. Also, be aware that certain sinus conditions can mask as tooth problems.
Just as the location of the sinuses around the tooth can make you feel pain in the teeth when you have a sinus infection, the closeness of the ear to the jaw can cause you to feel pain in your teeth when you have an ear infection.