I have tooth pain, sensitivity to cold&chewing , and swelling on a root canaled, capped, back, molar that was done in 2010. why am i having pain?

Wrong tooth: If tooth had a root canal there should never be any cold sensitivity. A root canal tooth with a problem can have sensitivity to heat and/or biting pressure. The cold sensitivity is from another tooth or the crowned tooth did not have a root canal. See a dentist to have situation evaluated, they should be able to help you.

Tooth pain: The cause of your pain can only be determined by seeing a dentist for a clinical examination and x-rays. You may have one or more problems and it may or may not be related to teeth and treatment already completed.

Pain and swelling: This needs to be seen by your dentist for an exam and x-rays to determine the cause. It could be a re-infection or a fracture of the endodontically treated tooth, an infection of another tooth, or a periodontal (gum) infection.

Possible infection: It is very possible that the tooth is reinfected or may have developed a fracture. Please have your dentist evaluate it.

Cold,chew ,swell sen: Obviously see a dentist! you have 3 symptoms, only two are root canal related. If you've had cold sens since the root canal, then i'd bet that tooth needs retreatment. If the area recently became cold sens then it's likely that the tooth next to it is involved because of new decay, tooth abscess or just a gum abscess exposing its sensitive roots. A re-abscess of the rct'd tooth could do same.

A few things: Root canaled teeth sometimes act up due to failed root canal, cracked tooth. May be another tooth. Seen dentist who did root canal for assessment.