Thanks for replying everyone 
I don't think it's pnd, I've had no problems bonding at all with LO or anything, it's just been a rough few weeks and it all just came pouring out I think. I'm fine now the kids are in bed, I'm just catching up on some laundry and bits and bobs.
DH is quite helpful, he'll put the elder two in bed etc if he's here, it's his comments that are getting to me, but it's not his fault, it's stuff I'd actually normally laugh at, I'm just a tad oversensitive at the minute.
I was feeling really anxious and my stomach was just a knot, it was as though I was waiting for something, I couldn't even go to the loo without one of them following me and climbing in the bath, pulling the towels down etc. everytime I stopped trying to get on to have a drink if I put it down for a second the LO would grab it and drink it. He was on the sideboard trying to get pictures off the wall every single time my back was turned, then screaming when taken down. My eldest kept talking, that's all she was doing, nothing 'wrong' but she would not stop, not for a second, and I had a house that looked (looks) like it's been burgled, a baby attached to my chest almost continuously, had to keep getting up and getting the 3 year old out the bath, out the kitchen, off the window sill, off the table, out the drawers, and he was throwing things and screaming, and the other was talking and I hadn't eaten/drunk/pee'd even and dh was working late again and there was no end in sight.
My 3 year old doesn't go to nursery yet. I'm currently battling to get him assessed as I'm genuinely concerned there's an issue, that he's possibly on the autism spectrum, amongst other things he's non verbal, which is partly where his frustration comes from I think.
So now how much worse do I seem? There's a reason for his behaviour potentially and I just wanted to hide from him and cry earlier. Some days, quite a few actually.
I think I need to calm down, stop worrying about the baby and allow myself to sleep, I'd probably be able to face the days better then.
No, I don't really have good enough friends to rely on. I thought I did, then she made friends with someone else. Silly as it sounds. I didn't bother again as it was too much like school, I didn't realise it was one friend and one friend only round here lol.
No family either, that's also sad, as I have close family members on the same street. But I asked for help a couple of weeks ago as I had a d&v bug, which made me feel pretty rough with BF'ing as well. I was really struggling, so I asked if they could have my 3 year old just for an hour while I tried to stop throwing up and got some fluids back into me as I was home alone with him and the baby, but they'd had a late night and was going for a nap 