Inform your dentist. I suggest you inform your dentist. They need to re-examine you more closely. X-rays alone may not indicate pathology such as tooth nerve pain. Explain to your dentist when the pain started, how it starts, and how long it lasts. Be as specific as you can be. Then they can evaluate you better.
Teeth pain. We can't answer on the internet. There are so many possibilities. A history and exam will guide the treatment plan.
Reexamine. X-rays are a 2 dimensional representation of a 3 dimensional object. They aid in diagnosis, but are sometimes not definitive. Ask hour dentist to reexamine you. Over time changes occur and you may need new x-rays of problem area as well as other tests.
May not be dental. If the x-rays and examination did not show a tooth problem, it may be something else. It could be, among other things, a muscle or nerve related pain. I would suggest seeing a facial pain specialist if your dentist finds nothing wrong.
Sometimes gums. Since it is difficult to know based on a question it would seem like you may need to go back to your dentist or see a periodontist or endodontist. Did your dentist measure your gum pockets? If so what were the numbers? Gums can cause pain in some cases.