Hi embracinglife. First off, congratulations on getting a job!!! And a job that is a good fit!! That's exciting!!
I have a lot of anxiety issues so I definitely know what an ordeal it can be dealing with an Anxiety Disorder. But in this situation I'm just thinking that it's actually pretty "normal" to feel nervous about starting a new challenge like this. If this is your first full-time job since leaving school then that is a big deal.
I definitely don't mean to minimize your anxiety in any way though. Just, I know that in my case I sometimes forget that everyone feels anxious sometimes. Is the anxiety so bad that it's making you physically sick or preventing you from sleeping properly or making you cry a lot? Do you have a history of anxiety? Do you have a therapist who you could talk through some of these issues with?
In any case, I really want to wish you well with your new job!! Let us know how you get on. Best of luck to you ((((((embracinglife))))))