Do you have any staining on any of your ceilings? Could it be caused by leaks perhaps coming from your roof? It won't get better by itself and will be causing more unseen damage as time goes by. Water will travel and find the weakest spot.
The first thing you should get checked are your gutters. If they are not clear there is nowhere for the water to go. Pick a rainy day, grab your umbrella and spend a few minutes looking at your guttering. You should not be seeing any water spilling over the top or drips coming from the joints between sections of guttering.