I've been away for aaaages so I know I've missed loads but just had a quick skim read, and mammoth post coming up...
sassy congratulations! I'm so envious of you happy for you!
It must be very confusing for Jacob and Isobel so I hope Jacob feels better soon. I really feel that orlaith will be like that if/when we have another child. It must just be very strange and confusing as they've had you pretty much 24/7 for the last 14 months. I obviously can't advise but I hope you manage to work something out where all your children are happy. 
newmum dp and I have been through similar problems and have argued a lot. I was feeling very bogged down as it felt like I had total responsibility of looking after orlaith and the house, as well as having assignments and exams. I was just generally stressed and felt I'd kind of lost myself, and this was just not what I thought my life would be like at 25. I suppose part of it is feeling disappointed in myself for not having graduated and got a career. I gave it time, I kind of had this deadline of after orlaith's birthday, and if I still wasn't happy I'd move into my sister's flat. Bu things have got better. I had my exam the week before last and now I'm free from uni work for a few months. I've also started working once or twice a week at the pub I used to work in, and I'm about to take on more work in dp's business. DP asked me to work alongside him but I chose not to as I think we argue too much, but working on the accounts side means our roles are completely separate, and in separate rooms!
cinnamon I can totally understand why you're annoyed and upset. Do you know whether it was actually planned or if they just decided on the day? You really need to speak to him and let him know that you'd much prefer if he just told you what he was doing. He probably just didn't want to hurt you though and didn't think it was a big deal.
Orlaith is 13 months today, walking everywhere now, saying lots of words and said her first 2 word sentence yesterday (it was "where daddy?" as we walked downstairs in the morning), she seems to talk a different language, and is generally a dream to look after now! but still wakes a few times in the night, grrr 