(((((justmom))))))))
It can be hard starting back after a long period of time and I do understand it is not easy; the doubts and anxieties can be overwhelming but to some extent know that they are to be expected. Be kind to yourself knowing that with beginning of anything that this will be the case that they will be there. In time you will be able to feel comfortable in the new position as you master the skills it requires and
you will master them; you have mastered so many other skills in your lifetime, these are just a couple more. In time, you will no longer be plagued with the doubts and fears as they will go away. They really will.
Being prone to anxiety and doubts myself, I now will focus on each task and one at a time, because if I start thinking about too much about what is required of me, the anxiety builds more. If I can do what I need to do in the moment, the anxiety and doubts seem to be lessen or disappear. Deep breaths also help if I begin to get anxious or concerned as to how things are going. It is always good to ask questions too to help get the information you need or if in doubt, which will help tremendously with confidence as well in the position.
You have already mastered the first steps in getting out there: applying, interviewing, and accepting an offer. These many times can be considered the hardest part of the process and you have done so well! I think of the next part of starting the job as my new "to-do list", just like I would have at home, what do I need to be doing and how can I get it done(?). The same process you are already doing now but now will get paid for it.
You can do it! Take good care of yourself, hang in there, and good luck!