Is Extra Protection Needed While Being On Free Pill Week And Antibiotics?

I am on microgynon 30 pill, I have a urine infection and have to take trimethoprim 200mg just for 3 days (two tablets a day) I have taken my 2 tablets for today, however I am on my very last pill out of my microgynon packet, i start my pill free week tomorrow and will bleed on sunday. Pharmacist told me to use extra protection for 3 days im on antibiotics and 7 days after. However I will start my next pack next thursday so do I count that as day 1 when the hormone is back in me, or is it 7 days after i finish antibiotic even although ill be on my period? please help