How Long Will Sulfamethoxazole Be Effective In Reducing BC Pills Effect?

I was treated for a UTI starting Friday, April 2nd. I was prescribed 800-160 MG of Sulfamethoxazole. I believe my last pill was taken Monday morning, April 5th. I know that this drug has shown in a small percentage of women to lower the effectiveness of the birth control pill. I am currently on Ortho Tri Cyclene Lo and have taken it regularily throughout that time. I just started my placebo pills yesterday. I practiced safe sex w/ a backup method of birth control while on and until the current date of taking the anitbiotics. When will I be completely protected again? It just makes me nervous because this whole week I will not be receiving the hormones and I am not sure with taking the antibiotics in the middle of my pack, how that will affect it. Am I protected right away at the beginning of my next pack?