My Boyfriend Is Having A Sharp Pain In His Lower

my boyfriend is having a sharp pain in his lower left abdomen closer to the Groin area he has been to a doctor and they don't know what it is his friend said to try and change his underwear but he's so skinny that new ones don't fit right but the doctor won't answer his calls and won't tell him anything what could be wrong and what can we do to treat his pain because pain killers don't really help