Tooth pain+sensitivity to cold. had a filling a month ago. xrays looked fine today. cold air hurt on tooth too. what else could be causing this pain?

Not uncommon or....: It's not uncommon to have some sensitivity for awhile following a new filling, and more likely to occur with deep, large, and amalgam filling. Other possible causes are gum recession exposing the root surface and the bite being slightly off. It should be getting better rather that worse or the same over time. If not, return to your dentist to have check it out or some other adjacent tooth problem.

Possibly pulpitis: Some sensitivity after a recent restoration is not abnormal such as fleeting thermanal sensitivity. Howevefr if you have unstimulated pain or are awakened from sound sleep by tooth pain you should return to your dentist or contact an endodontist.

Tooth pain: Whenever you drill a tooth, it causes trauma to the nerve which causes inflammation (pulpitis). It can take between 6-8weeks for the inflammation to subside. When you have a filling placed on a tooth, the pain/cold sensitivity should decrease over the weeks which is called reversible pulpitis. If the pain stays the same or increases, you have irreversible pulpitis and may need a root canal.

Root canal: If tooth pain persists, you may have irreversible pulpitis which would require root canal. Keep in touch with dentist to help decide course of action.