16/ f pulse in stomach, had it years. increases and decreases in speed. left side feels quiet wide can't really feel ends also i'm thin. is this nor?

Probably normal.: it is not unusual for young people to be able to feel a pulse in their abdomen. It usually occurs in people who are thin, although people who are normal weight can occasionally feel it also. It would be a good idea to see your doctor and have your blood pressure checked, but it will probably turn out to be innocuous. Good luck.