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

It could be brought on by your uterus stretching. Try drinking more water, emptying your bladder and lying down to rest as much as possible. If it is abdominal pain and/or with any spotting/bleeding from the vagina, best to consult your doctor from some advice. In all, stay relaxed and look out the signs mentioned by the rest. Seek advice from your doctor if you are worried for a peace of mind. Very important to stay relaxed and happy at this stage! Take care!!