I've taken a little while to come around to being excited with most of my pregnancies. Just my nature, I think. Not that the baby is unwanted at all - just a big mental adjustment to being pregnant again, and going through the whole process again, etc.
It will be OK. It is a big adjustment, and it does take a little while for your brain to switch tracks and think about a different future, but it will come. Give yourself a little time. Soon you will be thinking about the joy that the new little one will bring, and the fun of picking out baby things again, and watching him/her take their first steps, and learning words and so on.
As for the fitness - KEEP EXERCISING! There are some great prenatal DVD's available, and there's stuff you can find online too. No need to give that up. You'll have a better pregnancy, easier delivery, and a faster recovery.
All the best!