If the damp seems to be at the bottoms of your walls, then it is likely that the damp is the result of your damp proof course being bridged or faulty, resulting in rising damp.
If it is the case where the damp proof course has been bridged, it may be due to an external feature that has been installed, for example, a patio or a flower bed. Removing the new external feature or lowering the ground level and allowing your damp area to dry out, could solve your rising damp issue.
However, if it is that your damp proof course has failed, you will need to consider repairing it. If this is the case then you will need a qualified professional to fully evaluate the extent of the failure to determine the next steps.
Rising damp only occurs on the ground floor as it is moisture from the ground that is being drawn up into the walls, if your damp is on the first floor or above it may be that you have a condensation problem, or a penetrating damp issue.