neuroticlady, you've had so much good advice and support on here, but I want to add one more vote to the "yes, this is completely normal" pile. Unfortunately my Aussie friend with kids has moved out of Sydney or I'd put you in touch...
We had a terrible time with DS1. He had quite a traumatic birth and a nasty time of it in hospital, plus I was exhausted after a long labour, PLUS DH and I were both very young and totally without a clue as to what we were doing. In fact, DS1 used to get a particular look on his face at especially bad moments which we read as, "OMG - who are these total novices?? Somebody help me!!"
Anyway, my thoughts, for what they're worth:
Sleeping when the baby sleeps is VERY VERY IMPORTANT. I didn't figure this one out until my third. The temptation is to run around doing all the stuff it's hard to do with a baby in your arms. Just don't - it'll keep - sleep is far more important.
If you are the sort of person that finds it very stressful to be surrounded by mess, try finding one small area or job (the kitchen sink, the coffee table, the washing up...) to focus on. Make sure it's done, and then pat yourself on the back extensively once you've done it. For some people, the feeling of being out of control of the housework is actually very draining. And if you're not one of those people - you have the full permission of the many people who have posted on this thread to let it go
Do be a little wary of people who say, "It will all get better at x point in time" - because if it doesn't, you may feel worse. Babies (not to mention parents) are unique, and not all of them figure things out at the same rate.
Trust how you feel when deciding what to do. Really. By all means read baby books and pick up tips, but don't feel the need to follow it to the letter if it's not working. Not all methods work for all babies, and you are the best judge.
Getting out of the house, even if only for a trot round the block, is a great idea. And if you can get as far as a mother-and-baby/toddler group, even better. As a rule, mums like nothing more than a lady with a newborn baby we can coo over
Remember to eat regular meals and drink plenty. Sounds obvious but so easy to forget. Being hungry can also make you feel low.
It is still possible to cuddle up to your baby for a formula feed if BFing really hasn't worked out for you. And it does have the not-insignificant advantage that you can give a bottle to a friend or family member and get some extra kip.
I also second what Meeely2 says about walking away when it gets too much. It will not harm your baby to put him in his crib our of earshot for five minutes while you calm down if it is all getting too much. In fact, sometimes it can be a positive help to the baby, if the root cause is overstimulation.
Possibly not true for everyone, but we underestimate massively the amount we needed to burp our baby, and mistook an awful lot of windy cries for hungry cries. So do always consider this as a possible cause of crying; also try different styles of burping, as some babies are more possessive of their tummy bubbles than others...
Definitely warm up the sheet before you put the baby down if you can, and even better, put something in his cot that smells of you. We used to tuck a muslin across the mattress at head height to catch any night-time possetting, and I usually carried it around tucked under my top until it was time for the baby to go down. Swaddling has also worked well for us, particularly if you cuddle the baby for a good few minutes after he's swaddled so he warms up and feels secure.
Finally, PND. Probably different for everyone that's had it, but what worked for me was talking - not to a trained therapist, but to my health visitor (not sure if they have those in Australia?), who was simply incredible. She also arranged for a nursery nurse to come round once a week for an hour or so when things were really bad, to give me a little bit of space to sleep or just put my feet up and have a cup of tea and a read. I did eventually go on ADs, but at a very low dose; they made a big difference, got me over a bump, and coming off them was a lot easier than I had feared.
Good luck, and remember that we are all rooting for you!