I have pain in my upper left molar that is sharp and pulsating. i dont have a fever. how can you tell if its infected or not? i checked my gum.

Decayed molar: Possibly also infected. May need root canal treatment or antibiotic or both. You do not need to have fever or check your gum , sharp and pulsating pain would be enough. See your friendly neighbourhood dentist in no time.

Tooth pain: the most common cause of tooth pain is infection/abscess. Please see a local Dentist for examination/imaging to confirm. If gums infected you may not see a change...examination required to evaluate. This will not self-cure, now will just taking pills result in a cure. Please see a Dentist before infection worsens.

Root Canal Therapy?: What you describe is most likely caused by a cavity effecting the nerve. A clinical exam and x-rays of the area will determine the cause of the pain and what treatment would be necessary to hopefully save the tooth. I would venture to guess that the tooth will require Root Canal Therapy if there is enough tooth structure to save the tooth. Don't wait... make an appointment!