After my Pet Scan I Had a Positive Pregnancy Test. Anyone been here before?

So, I'm pretty nervous right now. I know radiation isn't good for a fetus, especially in such an early stage of development. I have no idea how far along I am yet. Waiting to get blood work done to confirm my pregnancy. I took a test before my PET scan and it was negative, and my oncologist always takes blood and no pregnancy symptoms showed up until this week. My scan was on September 21, and I took the test October 5th. I am just so scared that I was pregnant before my scan and possible side effects. And there's nothing I can do now...Has anyone else been in a similar situation before?