Posture is a common problem and concern. Specifically, we all are trying to achieve good posture, or what is known as "neutral spine" positioned. There can be problems associated with an abnormal curvature as well as problems that cause the abnormal curvature. I would strongly encourage you to discuss this with your primary care physician.
The spine has normal curvature. It is comprised of four major parts, including the cervical, thoracic, lumbar and sacral spine. There are three natural curves in the spine -- the cervical curve, thoracic curve and lumbar curve. Theses curves form because of the 33 vertebrae (or bones) as well as the muscles, ligaments and disks that form the curves.
As for what can cause a problem in the posture, any of the above mentioned components of the spine can cause it. Problems in the bone can cause it, either because of fractures or because of malalignment. Muscle problems can also cause this, either weakness or injury
of the muscles. Sometimes strengthening muscles can help with posture if the problem is with the muscles. In this case, physical therapy can be of benefit.
Keep in mind that poor posture can worsen over time. This is an important issue as if there is too much curvature can hurt internal organs. See you doctor
to prevent this. Good luck!