Pregnancy after Nexplanon

So I got my Nexplanon removed on March 3rd. I had it in for 3 years and it was expired. When I got it taken out the doctor gave me new birth control which is the patch you put on your body. She also told me not to have unprotected sex for a while because my birth control was no longer in me and I wasn’t going to be protected. Fast forward to March 7th, my partner and I had sex with no protection and he did not pull out. I was in complete shock because he knew what the doctor told me and I also did not start my new birth control. Ik sperm can stay in you for up to 5 days and that also has me a bit paranoid. It’s now March 23 and I haven’t had a period or anything. I’m also not sure when to take a pregnancy test since I technically haven’t had a regular cycle since before birth control so I wouldn’t know when I am ovulating or anything. Should I be concerned? How likely is it for me to be pregnant ? And has this happened to anyone else?