Feeling stressed

Yesterday was a bad day.  I was feeling stressed and overwhelmed and sad, so i posted the following on one of my many forums.  Then people started saying, maybe I had signs of PND, which stressed me out some more.
I will reproduce what I wrote here, but am happy to say that I am feeling much better today, and me and the kids have been for a long cycle ride/walk, had pizza hut buffet for lunch, and am now back home having fun.

I've feeling sooo stressed and frustrated and sad and angry atm. And the worst thing is I keep taking it out on DD1. It's not helped that she keeps winding me up and deliberately going against what i have said - but then she is only 3 still. I'm overtired, running on empty and i know i snap when I haven't had enough sleep. Again, DD2 ended up in bed with us last night, and was screaming and howling for far too long. Even magic BM isn't working atm. I don't know if she's teething (she was showing signs, but they've seemed to have stopped now) so I gave calpol which did seem to help. Then this morning, DD1 woke up at silly o'clock and starting shouting 'help help' and ended up waking DD2. She always does that for attention, and doesn't understand the consequences, even though I keep telling her not to should 'help' or 'emergency' . She's too young to understand Peter cried wolf, and as I have bad memories of it, I don't want to introduce the Matilda poem yet.
So, all i'm doing is screaming like a banshee, getting myself more stressed, feeling carp that the house is always a mess, and I can't do anything right. DD2 has been screaming all morning, DD1 wants to do painting outside, so i said yes, as soon as she has put the blocks away. (There are toys all over the floor, and i've only asked her to put 1 away.) Cue more cries of 'help help'. She's 3 fgs, and has done it a million times before - she does not need me to watch her every second of the day, especially when i'm trying to do what she asked for in the first place!
So, i spend ages trying to get the table out of the shed. As you'd expect, our shed is a complete mess, and DH has dumped his bike on top of everything, and caught the pedals round stuff, so i can't even move it. I eventually wrestle the table free, and think i'll set up the parasol (that we bought last year and never used) so DD2 can be outside too. So, i find the parasol base, eventually manage to wrestle the small table free (to stabilise the parasol) and somehow manage to lift DH's bike and tent bags and DD1's bikes all at the same time to squeeze the still-boxed parasol out from underneath everything. I put it on the grass to set it up, and immediately gets swarmed with ants (we've about 6 diff nests in the garden), so I move to the patio. The parasol, doesn't fit into the base we've got. DD1&2 are still screaming inside, through all this. Anyway, I try to set the parasol up, and the sodding thing has bent so the umbrella bit doesn't fit into the pole. It's never been used, and i feel carp. I've had a look on argos thinking i could take it back for an exchange as i still have all the packaging, but i think that because it's from last year, the catalogue codes have changed.
so i come back inside, and DD1 hasn't put a single block away, and is still shouting help. DD2 is still screaming, so i sit down to feed her, and DD1 goes outside, and i explicitly say not to touch the paint stuff until I go out there. Then I here 'mum, mum, the paint as spilt'. She's opened all the bloomin bottles (there's only 3 there) and split them all over the floor. I haven't been outside yet, as DD2 is still feeding, and just hope that she hasn't got paint on the parasol as i'm hoping to exchange it. So I'm still screaming, and i want to cry. I'm doing my best, but clearly my best isn't good enough and i just feel so rubbish. I can't see a way out of me feeling like this. i feel like I'm running up a down-escalator and not going anywhere, but if I dare stop for a second, things just get worse and worse. And I know I spend too long on forums and things when i'm stressed, which doesn't help matters, but it's an escape, especially when everyone is screaming. And on netmums there was a thread about a lazy SAHD who only had 2 kids to look after, and couldn't even manage to keep the house tidy, and all these bloomin perfect mums who have a million kids, a proper routine, spotless house, dinner on the table for when OH walks through the door etc etc etc, all suggesting the OP kicks her hubby out! He does more than me, so I must be truly rubbish. And i keep living in a dreamworld, dreaming ridiculous things, wishing my life were different, when i should really get off my backside and do something, but i'm too lazy and stupid to do anything about it. Meanwhile, I'm back here again, ranting away in my own self absorbed thread, whilst DD1 is yet again 'cuddling' DD2 (ie pushing her to the floor) and 'patting' (hitting) her whilst DD2 cries and i feel out of control of the situation. I was going to suggest DD1 invites nextdoor round (they've 3yo twins, and we go round there, but they never come round here) to do painting outside, but the room is still a mess and i want to cry. And after all that, i don't even feel better, just sorry for myself. sorry. And my temper is getting shorter and shorter, and i'm getting more physical with DD1 which I don't like (like grabbing her arm when she goes to hit me or DD2) and now if I tell her off she's started shouting back "don't hit me" which makes me feel even more carp. And it's not helped that DH (who suffers with anxiety depression) is wishing he never took this job as he hates it, and wishes he worked where he used to, even though their jobs are on the line every few months. I wish i could be content and happy and useful.Sorry for the moan. i don't feel like I can talk to anyone in RL about this, because everyone seems to be better than me and i'm so embarrassed. I can't even get my house together for when people arrive expectedly, let alone if i don't know about it in advance. My mum thinks we live in a pigsty, as does DH, and i do try, but obviously not hard enough. I've got so many things going on atm, even with this mammoth ramble (sorry about that) i haven't got half of it off my chest. I need to blurt it out, i'm not expecting anything in return.

As I said, I'm feeling better now.  It's good to know that i'm not the only person who feels like this sometimes.  And in turn, if you're reading this, it's good for you to know that other people (ie me) feel like this too sometims.