Namechanged for here... sorry this is probably going to be very long but I need to get it off my chest before I go nuts (or more so than usual)
I've had depression on and off since I was 16 - the first time I had crap counselling and it resolved itself when I went to university; the second time I had great counselling and it got better from a very scary position in a fairly short time; and then after a stress-related spell before maternity leave, it came back with a vengeance after DD was born.
It took ages for me to be diagnosed (everyone assumed I was just tired) and even longer for me to get a referral to a counsellor, so DD was almost six months old by the time I saw the counsellor for the first time. I was hearing voices telling me to self-harm or take an overdose, felt constantly that DD would be better off if I died and didn't usually stop crying from mid-afternoon until long into the night. Things improved a bit when I went back to work and the voices became less frequent, but there were still some scary episodes where I had to really fight off the urge to self-harm (usually over a small thing like breaking a plate or DH noticing the house was dirty)
Anyway, unsurprisingly everyone started to let me know that they were finding it all really hard - DH says he can't cope with me being miserable and upset, my mum says she's losing patience with me and I don't dare even start to reveal to anyone else how miserable I feel.
So, in the absence of anything else, I started to keep myself phenomenally busy so I wouldn't have room for reminding myself how worthless I am and could at least say that although I'm no fun, I can't play properly with DD, I'm a crap friend, a crap mum, a terrible IL and generally pretty thick, at least I can be useful. I also tried laughing whenever I felt like crying - a really false laugh like "Oh, ahahahahah! Isn't that funny how Mummy's just knocked something over even though it really hurts! Hahaha!" I don't ever believe it for a second, but always had this sort of hope that I'd really find everything funny eventually IYSWIM.
So DH comes home not to a crying mess but someone who won't sit down until collapsing exhausted at 10pm; my mum has a happy-smiley-jolly-isn't-everything-just-wonderful daughter that she wants, and I know I'm going mad.
I had my final session at the counsellors today and she was really shocked. Apparently she thought I was doing pretty well, had a really strong bond with DD and was a 'natural' at this motherhood business and had no idea of the extent of my depression until now. It seems like the one thing anyone thinks I'm any good at is hiding the depression... shame I'm not much cop at anything else really 
The thing that scares me witless is that now I've let the mask slip I have no idea how to put it back again.. I've almost lost DH to being a miserable arsehole, my mum would stop speaking to me if she knew how miserable I was and it's hardly fair to DD to bring her up with someone who isn't happy.
Sorry to witter on like some sort of verbal incontinent. It does get better... doesn't it? 