I don't know if these next words will be a comfort or not, but when I was in school I remember one of my down to earth professors saying that when he first started as a therapist (working in peds, if it matters), it took at least 2 years before he started to feel confident as a therapist. And, if I remember correctly, it was at least five years before he was "fully confident."
Does your workplace offer any mentorship?
I'm less than a month into my first job. I'm definitely nervous when it comes to patients with diagnoses I haven't treated yet, but I wouldn't say that I go to work anxious each morning. It probably helps that I was hired at one of my level 2 FW sites, so I've got good relationships with my boss/coworkers, and they already know what level I am currently at and try not to overburden me (yet) with anyone super tricky unless they are around to give me a second opinion.