Yes, it's normal ... especially as you venture into distances you have not done before. It takes some time and effort to train yourself to be able to eat while riding.
Some tips ...
I always bring gels as an emergency back-up ... for when the nausea kicks in. They go down better than solid food and I've done some significant distances on a gel or two.
I use liquid nutrition. On a long ride, I usually carry a bottle of Ensure ... Ensure goes down really well for me and provides me with a lot of energy. I also make sure one of my bottles contains a sports drink (preferably HEED).
I nibble. Rather than trying to eat a whole granola bar or cookie at one go, I eat one bite of my granola bar or cookie, and then put it in my Bento bag. 10 minutes later I take another bite of my granola bar or cookie, 10 minutes later ... etc. Doing that is MUCH easier on the stomach.