I took time off work due to mental health issues and a psych hospitalization and going back was very difficult. I also didn't mention to others that while I appeared to be doing fine, inside I wasn't. I agree that it isn't appropriate to drag mental health issues to work but, like you, I felt like a fraud. I can recall feeling kind of lonely at work because of not sharing this major aspect with myself with co-workers. One help was that I have a good friend I called and talked for a few minutes (she knows about the mental health stuff and loves me anyway) when I felt like I was going to implode and I think that got me through the hardest times.

Work does take your mind off your 'self' and issues for spaces of time so that is the upside. I have been back to work for 13 years now and it got much easier for me but I had to push through a lot of the fear to get where I am now.

Been there. I know you are hurting. Hugs to you.