reading your post, i could have written that myself . i call it the duck syndrome because everything looks calm and ok above the surface but underneath i am paddling away like mad trying to keep afloat! i think it comes from having a family where you are programmed to keep what happens at home at home. one of the draw backs of abusive parents i suppose.
i too am pretty functional... well the brain is, body is slowly giving up though, but like you was able to hide a lot of things until i really broke down and my legs gave up the fight to keep working, 7 weeks inpatient and not being able to walk are a bit hard for people to not notice!
now i have a great network of friends whom all know a little about me but none know all the facts. they know i can't walk, some know i had a breakdown, some don't, but none know much if anything about my daily struggles etc because when i am not ok they don't see me as i stay in my home. i cover it by 'needing a duvet day to rest my bum' which is acceptable for a non walker, and using the time to answer emails etc for work. people who read my posts on this site probably know the most about me as i try to keep my personal stuff just that around others geologically close to me.