Hang in there. Pregnancy hormones should kick in soon. They say that your body craves about 10% more sleep when you're pregnant.
As for age - I was 38 when pregnant with difficult child 3 after a 7 year gap. My mother also had a 7 year gap before she had me, her last, when she was 44. She said that she enjoyed me the most as a baby because at last she felt she knew what she was doing and had the maturity and time to really enjoy parenting. All the others were at school so it was just us two during the day. I have (unusually, I'm told) memories that go right back to before I was a year old, although only scraps before 12 months. Much more detail of the first four years when my mother & I did a lot of stuff together. When she said she enjoyed being with me, I can vouch for it somewhat - although she did tend to use the radio to babysit me and to mask her location when she wanted to get on with the housework (and I was put in the playpen).
I found a similar experience with difficult child 3. I took more time with him, he was the baby I had the chance to enjoy, to just be at home with instead of being a full-time worker breastfeeding in the breaks. Because of my physical disability, I didn't do what other mothers do (and what I had done with easy child) and clean house as soon as the baby slept - instead, I slept when the baby did and woke fully rested ready to cope when he woke too. I spent time with him, I sang to him, I played with him, I talked to him - so when he was delayed in speech development and they told me he was emotionally neglected or not stimulated enough, I knew it was rubbish.
I thank my lucky stars that I was a stay-at-home parent for difficult child 3; if I hadn't been I really don't know how well we'd have coped when we discovered the autism.
He could have easily been a easy child. But he's not. However, I think he's a lot closer to a easy child than if I were still trying to juggle a job and the other kids all the same age.
We're now older parents. The first three have all either left home or are about to. Three weddings. Our holidays are now mainly three of us - me, husband and difficult child 3. We took easy child & BF1 on our last BIG holiday (New Zealand June 2007) but they were along as adults, as equals. It still felt like me, husband & difficult child 3, with another couple along for the ride. And July this year, a week in Port Macquarie - me, husband & difficult child 3. OK, easy child came along for a few days but otherwise it was just the three of us.
If it had been just husband & me, we probably would have been lying around the pool more on that holiday. But then - difficult child 3 was doing a lot of his lessons in the mornings in the holiday unit, then in the afternoons we'd go out sightseeing. Because we were thinking of difficult child 3's lessons, we went to places connected to learning in some way. difficult child 3 loves mangroves for example, and they have a board walk through mangroves in that area so we checked it out. If it had been just me and husband, we probably wouldn't have gone. I am glad we went. Other places - again, for difficult child 3's benefit.
When we have people visiting us, especially people from overseas, husband & I get a real kick out of showing them around and helping them discover our country. To see the place through a visitor's eyes is a privilege for us. And a young child - it's a very similar thing. Now we are seeing our country through difficult child 3's eyes and again, getting a kick out of it.
Yes, it can be tiring. Yes, sometimes we just want to put him back in the cupboard and take out the batteries for a while. But we have to soldier on. [husband is such a pedant - he just looked over my shoulder and said, "You have to take the batteries out BEFORE you put them in the cupboard." And people wonder when I say that Obsessive Compulsive Disorder (OCD) doesn't just run in our family, it gallops!]
You have some good support in place. I suspect Moonwolf is very happy about this and will be a big help for you. In many ways you are all helping one another. If this baby is a easy child, it could take some time to be sure.
A baby will keep you and husband young at heart and in mind, even while you think it is ageing your bodies. Just think - you will get to enjoy learning about your world all over again, through a fresh pair of eyes.
Enjoy!
Marg