i started using the birth control patch a week ago and i had unprotected sex the next day

You should keep in mind that it takes like at least a week for birth control to have its effect, month for 100% effects. So having a sex on the second day of your birth control is not such a smart idea. I hope your partner did not ejaculate inside of you. If he did not then there is nothing you should worry about. If he did, then you should definitely get tested. Just buy a home pregnancy test. Make sure you take it first thing in the morning and make sure that It has been at least 10 days since your last unprotected intercourse. Hope this helps.