I need some suggestions from someone.

I am having tooth pain on the left side of my face. The back 2-3 teeth.
And the jaw (left side) is tender (as if I have swollen glands). I
don't have strep throat or ear infections. This tooth related pain is
on the bottom of my mouth, sometimes and then sometimes it's on the
top (left).  There is no correlation to eating, drinking or sleeping.
Sometimes as I drive I feel an intense throbbing and my jaw feels as if
it's been chewing for hours.  The pain comes out of nowhere and
leaves within 10-15 min only to return again, at random. X-rays of the
bottom 3 teeth do not show abscess or infection.  Dentist only took 1
x-ray. Says maybe the root is dying but that's not showing. I am
taking penicillin and naproxen (for pain).

Ideas on what it could be? What I can suggest to my dentist?  Anything?

Thanks -- Mkatherine