Andrea,
The caravan wheel is attached to a swing arm which is in turn suspended from the internally rubber-sprung axle.
The rubber springs used in the caravan axle deforms according to the weight applied to it, and you can get an idea of the condition of the springing by imaging the axle and swing arm as parts of a clock:
Axle = centre of the dial
Swing Arm = watch hand
If the caravan is un-laden, then the swing arm should point to just below 3 on the clock face (just below horizontal)
If the caravan is lifted off the ground, then the swing arm should lower and point to between 4 and 5 on the clock face
If you really load the caravan to it's maximum (or if you hit a bump while travelling) the swing arm should point to 2.
So check your caravan - if you unload the caravan, the swing arm should be (just) below horizontal - and if yours does that - then the suspension system is fine.
Unfortunately the wheel will hide the swing arm, but if you get down on the ground and look under the caravan - you can easily see the swing arm on the other side of the caravan.
Robert