If I do not continue to use Evra patches, am I protected against pregnancy after peeling off the 3rd patch?

Hello. Soon I will start using Evra palstry. In the third week I will stick a third patch, and in the fourth there will be a week's break without a palstra. After the fourth week, I intend not to apply another patch, thus discontinuing this method of contraception. Should I therefore use additional non-hormonal contraception during the fourth week (without the patch) when intercourse occurs? How long am I protected from getting pregnant after the fourth week?