You sort of have the right, but they have all sorts of ways of taking it away from you. Courts, CPS etc can be used. They can declare you temporarily unable to make your own decisions and so on. It will depend largely on whatever nurse you happen to get, and if she likes you or not.
Now, you can take showers, if you aren't hooked up to a lot of machines, and short walks, and all that. If you don't make a lot of fuss about the monitors, but frequently ask to have them off for a little while, then hope they forget about you for a little while, you can sometimes get away with more than if you use direct confrontation. Things can sometimes escalate to a power struggle if you try to put your foot down, and the next thing you know you are strapped down for your "own good." I've been down that road before. That's why I wont' have any more babies in the hospital. I birth at home where I call the shots.
In the hospital I know I'll end with a c/s every time. At home, I can VBAC. My births take too long for the hospital, they just won't let it happen, and all the monitoring etc slows me down even more. Home is the only option for me, home or c/s.