Seat Altea XL advice please

We currently have an 07 altea xl which we have had from new and has been a great car. In October we became caravan owners matching with a sprite musketeer td, just under the 85% as we are newbys. We have taken the van out twice now and despite there being nothing in the van bar necessary gas , battery, the back of the car seemed very low, really riding on yhe bottom. Is this normal for this car? Or is there problem with the suspension? We are weighing up the options as we know we need to spend some serious money on it (cam belt, turbo, service, regas) shortly and don't know whether to cut our losses and get a new car instead.?