What are causes of belly on pain?

Ok. well I've been getting belly on pains for over a year now, but they're only from time to time after lifting heavy objects, or doing abdominal strength, its a sharp pain like if someone would be pulling some sort of string inward feeling like my belly is about to bleed but no bleeding hurts to get up or sit down, to use the restroom. the pain is from my belly to my oris, its only sometimes though.. please help!