Because I'm not remotely a mental health professional, I'm going to focus purely on the Workplace-related questions. Please don't for a second think I am ignoring or do not respect very real mental health concerns.
That being said, with the exception of your confident statement in the middle, you just described almost every good software developer I've ever worked with, for, or managed! (And a few bad ones, too.)
I'm going to address some of your statements individually:
- Decisions made at managerial levels above you are causing you to be consumed with worry and anxiety. -- How are these decisions being
communicated with you and your peers? If your managers are dictating
from on high, and they are not welcoming input or discussion, I'd be
stressed out, too, especially if I am a developer who can see the big
picture, who interfaces with clients, and who has a desire for
positive outcomes for everyone. In other words, you care. This is
good. Tipping over into all-consuming worry? Not so good, but sometimes
not entirely your fault -- if I, as a manager, didn't constantly
communicate with and not to my employees, I'd expect to face a
stressed-out bunch. So, stop for a minute and think: are you
worrying because something is unknown because your manager is a bad
communicator? Don't own that worry, if that's the case. Confront it
and make the manager be better (you said you like to coach, yes?)
- Your boss and coworkers have noticed and might think you're weak, which makes you feel worse. -- Is this a perception, or have your
boss and coworkers actually come up to you and said "suck it up,
weakling!" If your boss hasn't, and this is a perception, go talk to
him or her immediately and get the facts out in the open. You can
only work positively with facts.
- You confidently stated the things you are good at (turning around
failing projects, coaching and guiding people) -- weaklings don't do
that. Actual weaklings, and people who have little to no utility as
leaders, tend not to find any positive factors about themselves or
their work. You give yourself the credit you are due (and, to
localize this answer for a moment, given the questions and answers
and engagement you show on Programmers.SE, you absolutely should give
yourself this credit). This is a good thing. It is clearly done
without arrogance, and with confidence, which is an even better
- You think you have shortcomings -- Yep. You probably do, just
like we all do. Dwell not on those, but on all the positive things
you know are true. Work on your shortcomings, here, with a coach,
whatever the case may be -- just like you like to coach others, let
someone else coach you. It's why they (and mentors, and good people
on SE) exist: because we all have shortcomings and we all
consistently work at getting better.
- You worry about irrelevance -- I find this one amusing, because
in my experience, managers are the first to go. I've been through
all the booms & busts, and it's not the developers who get tossed
aside first. And it's not the out-of-work managers who can name their
price in the next job: it's solid, thoughtful, productive developers.
Usually the ones who worry too much, too. The ones who care.
Like others have answered, have a discussion with your boss, especially if communication is poor, and especially if you have a diagnosis of an anxiety disorder of any sort.
If you have not had any official, negative performance evaluations, then your conversation can go something like "You see my productivity and value to the company and my peers? Well, I'm stressed out to the max because of X, Y, Z. Can we work together to mitigate that stress in some way?" Managers worth their salt will have been trained or at least had discussions with HR folks to address these concerns. A blocker that is all stress is no different in its need to be cleared than a blocker that is technical in nature. Your manager should work with you to clear blockers. If you have had official, negative performance evaluations, then your manager should be working with you on a performance management plan that will enable you to succeed, not punish you for having the brain that you do.
Either way, that conversation is not a sign of weakness; it's a sign of maturity.