Oh boy - I feel for you! I can't say whether you do or don't have PND, but you are saying many of the same things I felt when I first had my (so far only) baby nearly 18 months ago. I immediately suffered from massive anxiety and as you said, was stressed out by everything, big and small. And after the first couple of months, my sleep was a nightmare - a waking nightmare at that. Even when baby did sleep, I didn't, and I got to the point where I'd fall asleep at 9/10pm then be awake from midnight feeling dreadful and panicking about the fact I knew I wouldn't get back to sleep again until the next night. I was so tired, but at the same time completely wired and just unable to sleep. My doctor also tried me on sleeping tablets first (zopiclone) but although they put me to sleep, they didn't keep me asleep and I still woke up a couple of hours later. My anxiety got so bad, probably with associated depression (although it's hard to tell, particularly with the lack of sleep - cause or effect?) and I was given antidepressants (citalopram) which were a complete godsend once they'd kicked in. Two months later I was back to my normal self, personality wise, and gradually my sleep has gone pretty much back to normal. I was only on them in total about 8/9 months and haven't felt any need to go back to them since.
Post natal insomnia is actually really common, and not just because you get woken up by the baby. Some biological switch seems to happen in a mum after birth where you are somehow always listening out for your children, even when you're asleep, so you never seem to sleep as deeply as you did before they came along. And for a number of people, it can wreck your sleep completely. Do a search on here - there were a couple of really useful threads on it from a few years back.
Insomnia and anxiety are also major symptoms of PND, so that might be what it is. But then losing sleep and worrying are also major symptoms of parenthood, so that might also be what it is. I don't think it's really important to define or label yourself, but what is important is to find ways to get through this. PND (and all depression) leads to changing thought patterns so that things that wouldn't normally have bothered you get blown up into major worries, and some of the things you're saying resonate with that - as do things like not enjoying things any more and feeling like things are out of control. I think you should continue to seek help with your Dr if the sleeping pills don't kick start your normal sleep routine and that doesn't in turn make you feel more like yourself again. Counselling can be massively effective (CBT especially for anxiety) and antidepressants were amazing in my case.
As far as the insomnia goes, there were a few practical things I learned which really helped. Firstly, never look at the time when you can't sleep. It doesn't matter how long you've slept, and all it does is give you something else to worry about to keep you awake - "I've only got x hours until the baby/toddler wakes up, I've only slept x hours" etc etc. None of it matters. Just fuel for more worrying. It's a really really tough habit to break, but trust me - put all clocks out of view and just lie down and rest. You can feel whether you've had enough sleep by how tired you are. The numbers are just a worry. Secondly, do remember that the worst thing that can happen if you don't get enough sleep is that you'll be tired. And you know you can survive tired. I got so stressed out about sleep and totally hung up on it. But really, the tiredness was totally manageable once my mental health was back on track. What you said about not wanting to go away in case the children didn't sleep really resonated with me. too But now I see much more clearly - what does it matter if they don't sleep? So you'll be tired. You're tired now. So it won't be any worse than now. There's nowhere worse for it to go! But by being away, you might all feel a bit refreshed by the change of scene. And facing things that make you anxious can help you get over the anxiety - so pushing yourself slightly out of your comfort zone then seeing that the world doesn't end, will help you to push the boundaries again the next time.
Am I making any sense? I just really wanted to let you know that although what you're feeling is not "normal", it's very common and it will go away. It really will. It might need (medical) help to go away, or it might go away on its own, but you will get through. Don't beat yourself up about how you're feeling. Lack of sleep isn't used as a torture device for no reason!! But I would definitely suggest you get as much help as is available. Why suffer if something simple like talking to someone or taking antidepressants might actually make all the difference? xx