Why when i swallow it hurts my ear?

Eustachian tube: When you swallow, a muscle opens the tube that communicates to the middle ear space from the back of the nose.(eustachian tube). This is a normal physiological process that equalizes middle ear pressure to outside pressure. If this process hurts, there is probably some inflammation in either the throat, back of nose, or middle ear. Swallowing should not cause ear pain. See an ENT doctor.

Referred pain: You can get referred pain from a throast problem, causing ear pain when swallowing. If it has been there for a while, see ENT doc for exam.

Could be neurologic: Hypoglossal neuralgia is a rare entity that causes jaw and ear pain stimulated by swallowing. A trial with anti seizure- type Rx supports diagnosis if it relieves the pain. Often there are no objective findings on exan or MRI. Surgery and special type of radiation are curative. See a neurologist if no diagnosis from ENT