Hi Hazel! I remember feeling the way that you did while pregnant too. It really kicked into high gear when I was in the check out line at Babies R Us (swaying side to side while waiting to pay as all pregnant mommies do;-)). Anyway the woman in front of me paying had a 2 year old and a 4 month old. The 4 month old was asleep in the infant seat attached to the cart and the 2 year old was in the basket part of the cart screaming to get out. The mother gave in to the 2 year old since he started dangerously trying to jump out on his own while she was trying to focus on checking out. The mom pulls out her wallet to pay when the 2 year old takes off running to the exit door. The mom shouts for him to come back as she is handing the woman the money and he continues to run (almost out the door now). She drops her wallet on the counter, her money falls to the floor, and she runs to get the two year old. She bangs the cart as she runs and the baby wakes up crying. So now she is 20 yards away chasing her son, her little baby crying and unattended, and her money on the floor. That was when it occured to me how scary it can be.
Anyway, as far as adjusting, before Kyle was born we gradually introduced Eric to his new "big boy room and big boy bed". We made it fun and colorful and it started out that he just liked to play in there, then nap in there, then sleep in there a night or two, and finally he just treated it as his room entirely. Then when Kyle came he didn't see it as he had to give up his old room and crib. Then we also got a few of his favorite snacks and an Elmo and Blues Clues tape and said it was what Kyle bought for him for being such a fun older brother. These are ideas passed on to us and I'm sure you have heard them too.
Also, we found that Eric gets frustrated because he wants to feed Kyle and hold him. We allow him to do this occasionally (supervised of course). My OB suggested that I buy a slurp and burp doll and let Eric feed that baby doll while I feed Kyle so that he can do what mommy does and feel included too.
After having Kyle the first three weeks were the hardest with Eric showing signs of jealousy and lashing out, sometimes at Kyle and sometimes at us. But now he seems to realize that Kyle is staying around and he loves to kiss him and help me with him. Yes, we still have a few temper tantrums (ie, Kyle cries and Eric drops to his knees and cries too competing for my attention)but we are getting through them.
Right now I say enjoy your sleep while you can. It does get harder with the little one waking up a few times for feedings and the older one sometimes waking up too, making for some long sleepless nights.
Good luck to you and keep us posted
!