If you suddenly develop stomach pain at night and it doesn't go away then you could have some health issues such as Irritable Bowel Syndrome, Stomach Ulcers or other digestive issues.
If you continue to suffer stomach pain during the night you should speak with a doctor to find out exactly what is going on because normally you should not have any stomach pain at night.
Other causes of stomach pain at night could be eating too much food before bed, eating foods that don't agree with your stomach or you could have the stomach flu.
You could also be experiencing Acid Reflux disease that is only flaring up at night.
You could also have a bowel blockage, constipation or even other intestinal issues so I would highly recommend seeing a doctor or going to urgent care if the stomach pains continue for more than one night and don't go away within a few days to a week.
Sometimes it's nothing serious when experiencing stomach pain and other times it can be caused by some more serious health issues.
If you're a female and have your period then it could be the cramps at night from your period which is normal.