Hello Helen, You certainly shuld be able to uncouple car from caravan much more easily than this. If you have the type of hitch with a built in stabilizer ( Al-KO is the most common and has a dull red housing) then make sure you have pushed this handle to the upright position and fully forward. Then there is another small handle which need to be lifted up to about 45 degrees to free the ball. Most people hold this handle up with one hand while winding down the jockey wheel with the other.
The third reason for faling to disconnect easily is that the hitch damper is either still compressed or has been over-extended. You can tell which by looking at the black rubber (tubular) gaiter which is immediately behind the hitch; note how it looks when the caravan is not connected to the car - this is how it should look when you are trying to disconnect. If you have reversed the van onto the pitch with the car, then there is a fair chance the damper will remain compressed. Put the handbrake of the van on, and then very carefully more the car in the appropriate direction - it will only need to be an inch or so.
My present van is the first I've ever had with a built in stabiliser in the hitch, and I have noticed it is much more important to get the extension right with this hitch than with any other I've had.
Sorry if you have already been doing all of the above - if so post again and we'll get more experience applied to the problem.