probably not properly watered in, (none are done correctly). Your home was either built during a rainy season or during a time without rain. Either lack of or abundance of water has made your foundation or better still the earth rise or fall.
What area of the US do you live in? If you are in an area with clay soils you need to begin watering your foundation.
This is not uncommon on new homes, they will do this for quite a while then settle down and stop. You will find that the cracks will close up in the fall and winter and then re open in the spring and summer. If you fill in the cracks, use a latex caulk and force it into the crack then paint over it. The latex will expand and contract like a rubber band and hide the area for a while.