Thanks for using the forum.
Without knowing your history, or how far along you are in your pregnancy, I can't tell you what is causing your discomfort. There are many different discomforts and pains that can be normal parts of pregnancy. As the body changes to make room for the growing baby, it is not unusual to feel some cramping. Round ligament pain is a sharp pain in the lower abdomen usually felt when sneezing, sitting up, or rolling over. The pain is caused by hormonal changes to the round ligaments to allow for the growing uterus. However, if you are concerned, I always recommend speaking with your doctor. It is often hard to tell what sensations are a normal part of pregnancy, and what to be concerned about.
Congratulations on your pregnancy!
Cathy