Congratulations on your pregnancy!!
Along with the other posters I too will confirm that its normal to feel this way!
I had wanted to start trying to a baby long before my husband did and when he eventually said he was ready we started trying. We fell pregnant and my first reaction was "Oh sh*t!!". He was over the moon, but me not so much! I eventually got very excited but it was a big shock.
Being a parent is so tough, but it really is the best aswell! My little one is now 15 months old and throughout her life there have many times that I have been overwhelmed and over it. Don't even be afraid that you are the only one if you ever start to feel that way, I did and many friends confirmed that they too had felt this way. There are so many people out there that you can speak to
Your life will definitely change but thats not a bad thing! Maybe in the next 9 months do lots of exciting things with your partner, go out to dinners, movies, away, spend a day in your PJs watching movies, just be together doing whatever you both enjoy. Also make time for one another when the baby is here - some days will be better than others. BUt you can make time, babies sleep alot!
Goodluck with everything!!