It would probably be better to at least call your dentist. Doxycyclin may not be the antibiotic of choice if the tooth under the crown has now become infected.
It would at least warrant a call. Please don't wait out the two weeks. Infections can become incredibly nasty in a short period of time where a phone call may solve the problem.
Please don't put this off.
My best to you,
I agree, this can't wait two weeks.