I think i may have a scaphoid fracture, but i'm not sure. how can i tell what is wrong?

Can't tell: It is very unlikely that a person can tell if a bone is broken. It is also unlikely a doctor can tell just by examining you. Even an xray will occasionally not see a hairline fracture. Pain is a very unreliable criteria. Moving whatever part of your body is hurt is also a very poor criteria. Bone sticking through skin is obvious. Otherwise an xray is needed if there is concern.