I agree with the Albatross. so many times in life we think we are functioning well, PTSD or not. You feel strong, you are coping, but really truly, you might not be coping as well as thought, then it hits you awhile later like a landslide. I'm not PTSD, however, many years ago. I had a major panic attack while driving down a major highway. Thought this was it, felt like a hear attack, tunnel vision, chest pain, tachycardia, sweating etc. Managed to pull off and get help. When I went to my family doc a few days later, he suggested stress. Now if you know me well, I am a type -Z personality. If I was any more laid back, I would be buried. When I reflected on what had been happening in my life in the previous year, I saw some truth, especially in a situation that had happened months before, and that i thought i had dealt with just fine, thank you very much.
I took short term disability. Then I was going back to work, modified. Walked in on a Friday, told them see you Monday, and as I was walking down the back stairs, knew that i wasn't ever setting foot back in that office.
Now my case is minor, everything resolved in a short period of time. Add to it the traumas that you have experienced, far worse than mine, and you probably had some built in short term coping mechanisms which may not have been ideal. Throw in the alcohol/drugs (subconsciously not coping as well as you had thought) and then one day, boom. Done like dinner.
As for the long term unable to work, I wish I had an answer, hopefully someone else will be able to help you. I'm still learning and gobbling up info. I know my guy has difficulties as well, it's been years. My heart as always goes out to you folks. I'm a fixer, and I can't fix this or even offer you a pat answer. :(