I've had on and off pain in one tooth for years. it will hurt when i put pressure or bite on it, and then it will go away and return months later.

Thorough dental exam: These situations can be difficult to figure out. Careful clinical and radiological exam will hopefully help you find out if it's a cracked tooth or a necrosing pulp or something else altogether. If the pain is gone for months at a time, it may be dental pain of non-dental origin, meaning referred from a non-dental cause. More detective work required!

Diagnosis?: The tooth requires further evaluation, at least by your own General Dentist if not by an Endodontist. In addition to a clinical exam and x-rays, it would be wise to have your dentist pulp test the tooth. That test is not always conclusive but may reveal that the nerve of the tooth has become non-vital. Your symptoms are often the result of a non-vital tooth that does not yet show that on x-ray.