To stop this from happening you can do two thing:
-The easy one: Select the objects/faces you want to texture and hit the apply button of the texture, now unselect it the the object/face will be texture even everywhere. The problem with this is that you cant move/scale the texture afterwards like with UV. It often gives a ugly result but somethings it will do.
-The harder one: Download an UV-map program like roadkill or UV-mapper, export your model, map it in the UV-mapper. Then texture it in your favorite paint program. This will give you the best result, but might be hard and cost some time doing it.