I've taken cyclobenzaprine myself for muscle spasms. When you first start taking, it might make you feel a little strange, and it can blur your vision a little. But as you begin to get use to it these side effects tend to go away. You don't have to be frightened of it, just be cautious. And don't drive or anything, til you get used to it.
I've never heard of anyone taking half a pill, but its probably a good idea until you get use to it. And hopefully, it will make you feel better.
Take Care
flexeril (I believe it's the same thing your dr gave you) is a good muscle relaxer. I haven't had too many wierd side effects other than the sleepiness and since it is not time released you can cut it in half if you need.
I'd suggest taking the 1/2 and if it doesn't work take a whole 10mg thing and see if it helps. Flexeril helps me better than the other similar strength stuff so I try to take it at night and then again first thing in the morning. :) I hope it helps you