Loseasonique and antibiotics?

I have been on Loseasonique for about a year and was recently prescribed doxcycline for a skin condition. My dermatologist told me that a back up form of birth control was needed until my next placebo week (8 weeks away, eek) but my gynecologist assured me that the oral contraceptive/antibiotic rumor was a myth. I usually only rely on Loseasonique and the pull out method but, being cautious, I do plan on using condoms as well while using the antibiotic. Now, the questions: how long after stopping the antibiotic should I continue to use my back up form of birth control? Has anyone had any specific experiences with either this birth control or antibiotic?