Does Keeping the Soil Moist Reduce A Shift In The House?

Ok, My wife and I purchased our first home three years ago. I noticed that lately the back door is not closing properly. There is a small gap at the top. I also noticed that the fireplace(Brick) next to it has cracks along the roof(Small but you can see them). I noticed the door closes better in cooler weather and when the ground is moist. I was afraid my foundation was cracked but someone told me that it could be the fireplace's weight or the ground shifting(I also noticed cracks in my backyard). I do live in Texas where the soil is always crazy. I hear a soaker hose around the edge of the house may help this? We are gonna be here for awhile but I dont have the money to drop on a foundation repair right now(Just had a baby). Any suggestions on the Soaker hose idea?