I had the post-birth high, too! I had a bad tear and believe it or not was singing as they wheeled me into theatre!
Bless you, Puppie, you poor thing. I do hope you start to feel normal sooner than you expect, but my advice is to be kind to yourself, both emotionally and physically. You can't predict how your body will respond to birth, and the experience may or may not leave you with a slow healing process. Just take it easy, look after yourself whenever you can, eat nice food (cook and freeze food before the birth - believe me this will save your life!! Then when your frozen store is emptied, just cook in bulk and repeat meals during the week).
Ask your partner to buy you a surprise treat once a week. Get lots of funny videos so you can laugh and relax (once you get time to watch TV!). Buy yourself an expensive body scrub and matching rich moisturiser (oh my word this was one of the nicest things I did post-birth). After 6 weeks do some post-natal pilates to help you start getting your body back in order.
Also when you're in hospital, if you're given any advice at all, ask the medics to write it down at the time they're talking to you as you prob won't remember it all. Also do ask 'why' they're telling you to do those things, as you'll understand better and will be more likely to follow their guidelines.
Oh, and when you've given birth, make sure you take a bottle of warm water in to the loo for your first wee - pour it down yourself as you go, otherwise it stings like hell!
If you have stitches, avoid long baths as it can interfere with healing.
If you breastfeed, you may be lucky and find that the weight melts off...but quite a lot of us find that our bodies retain the weight until we stop BFing. If you're in the second group, try to accept that things will happen for your body, but just slowly and gently. Then enjoy yourself again.
Oh, and if you BF and find that it hurts, contact either La Leche League or the NCT or a trained hospital BFing counsellor (though I think the first two groups are generally better). Many midwives sadly do not know what they're talking about when they offer BFing support, and in my opinion should not dish out advice on this matter. It's all the better if you have the BF counsellor's details before you give birth as you can just give them a call there and then.
And finally spend as much time as you can just relaxing and adoring your gorgeous baby (actually, nobody needs to be told to do that!).
Hmmm...not quite what you asked for, was that?!!
Good luck and have fun!!