I have had a broken tooth in #30 for 6 mo w/no issues. 4 weeks ago i began intense pain along with a horrible metallic taste. pcp gave rx twice and partially resolved. dentist today says there is no infection. still in pain!! did he miss something?

Intense pain 4-5 months after sustaining a broken tooth = infection until proven otherwise. The fact that it got better with Rx (presumably antibiotic) and then relapsed makes infection even more likely. See a different dentist. Now its “just” a pain - if it goes on long enough, it can get really serious.

See an endodontist to have that tooth evaluated. The infection may not show up on a radiograph if it has been treated with antibiotics

No way to answer your question without a comprehensive examination with imaging. Antibiotics will not cure a dental infection, only control its spread for as long as you are taking the medic action. This pro baby would have been an easier fix 6 months ago, but I'm sure you're already aware of that. Please see a root canal specialist, an Endodontist, for appropriate care.