Hello there ,
Thanks for writing your query,
Dental pain in an already filled tooth indicates the presence of infection below the filling .
indicates bacterial decay or infection in the tooth that involves the exposed tooth nerve tissues .
According to your history i can suspect some remnant of the infected pulp tissue has left unexplored during the root canal
procedure or there is a missed canal due to which the infection has gone worse and you have developed a periodontal abscess
due to spread of infection to the underlying tissues.
This type of periodontal abscess drains in the oral cavity and may lead to nausea and vomiting.
once the abscess is drained the infected tooth needs to be explored again for root canal procedure.
you need to get an x ray done the affected area to confirm the presence of infection, approach a dentist
for the treatment.
i would suggest you to start with a antibiotic and analgesic
course consulting your dentist , which helps in subsiding the swelling and relives pain.
i hope this helps ,