How can i tell the difference between anxiety and sporadic familial insomnia?

Almost certainly: Your sleep issues are almost certainly anxiety/psychiatric. Sfi is so incredibly rare, it's essentially unheard of outside of people google searching for it. See your doctor and get a referral to a good psychiatrist. Good luck!

Insomnia: Familial insomnia will be present for a long time and it will be a trait of yours, anxiety will induce insomnia when you started having it, the timeline will be a guide.