Connie
Transitioning to management/supervisor status will cause anxiety for many. Just remind yourself that you were promoted for a reason. Your superiors probably had good reason to give you extra responsibilities. As far as dealing with your subordinates, don't let things get personal. I am sure you have a procedure/policy manuals. Learn them and hold people accountable for their performance. This is now your JOB and I am sure it comes with a pay raise, which many people would trade their third molar for these days. If verbal counseling does not work with your subordinates, then document with a paper trail. Use your organizations email to document problems. Find a trustworthy person in HR, or your own supervisor to give you advice handling difficult situations. Act confident and you will perform well. Don't confide in anybody about your history of depression or insecurity. You are now the boss and you must master the process of management.
I am the Medical Director of a hospital pathology department. I deal with alot of technical managers who come to me for advice dealing with problem employees. Our lead transcriptionist was often ganged up on by those beneath her. My advice is always consistent. Stick to process, document, be confident and never take things personally.
Give yourself a chance before throwing in the towel. It can take months or even a few years to get a firm grip on your new job.
Keep reminding yourself that your superiors promoted you for a reason.