I am experience cramping sensation. I am only at 28 weeks now. Is it common? Am i at risk for preterm labour?

There are several factors that may increase the risks for preterm labor, such as previous history of having one, high level of stress or long working hour of standing up. Try empty your bladder. Lie down on your left side and avoid lying on your back. Monitor your contractions in one hour. Does it worsen or disappear? Look for other signs such as watery or bloody discharge,or lower backache that come and go or persistent. Contact your gynae if your cramps won't go away or you have the above signs and symptoms. Read more here for your reference: http://americanpregnancy.org/labor-and-birth/premature-labor/