Is it true that you can become resistant to doxycycline and than acne will come back worse than you started with?

It's unlikely. Since the Doxycycline is NOT BEING USED as an ANTIBIOTIC rather a non-specific ant-acne effect!! It IS true however that resistant organisms might develop and cauuse trouble elsewhere THUS it's a good idea to talk with your DErMATOLOGIST about alternative/complimentary methods to treat your acne! Hope this helps Dr Z.
Resist Doxy? Possible but best to discuss with a treating derma...