I had an ectopic for the first time confused

A.

I got pregnant right after getting off birth control (Nexplanon) but my gyn told me that they don’t know exactly what type of pregnancy it was. At first they believed it was ectopic/tubal pregnancy but when they did the ultrasounds they didn’t see anything. I was only 5-6 weeks along. Can anyone that has gone through something similar please give me some clear information. Should I be concerned? Thank you! 🙏🏼