Since you have identified the fear of being trapped, that should help. It sounds like you have a harder time when you don't have control. I'm similar with needing to be in control.
In that case, a MH might be a better option. Keep the campsite simple, don't use full hookups, etc. With a smaller MH, you can go and park and enjoy the outdoors, but you have that security that you can simply sit down in the driver seat and leave. Just knowing it's that easy can ease the anxiety.
Another thing to always make sure of is that you get enough sleep all the time. If you can't sleep in the RV, don't go overnight until you can. Even one night of no sleep can throw everything so far out of whack.