thanks for the query.
as you wrote blood oozes when you were brushing or otherwise it means your gums and teeth need a professional cleaning in dental office. this condition is GINGIVITIS
which worsens further into PERIODONTITIS
leading to tooth loss
in worst scenario.
or as your dentist
knows your history and seen your case clinically, so might be a possibility of abscess
under the very question tooth.
start brushing twice daily with mild brush in a circular manner.
use warm saline rinses (half cup Luke warm water + half tbs table salt). rinse with it every day twice after brushing.
stop medication and let the access opening of the tooth be done by the ENDODONTIST and let the pus drain out completely.
for sensitive teeth you can use CLINPRO from 3M COMPANY.
you need a professional help exact diagnosis and further treatment..