I'm about to join the military and i was wondering if they can tell if i'm masturbating.i haven't done it for 2 weeks and the test is tomorrow?

Wouldn't know: I wouldn't sweat this. They don't care if you have self or partner sex before your evaluation. As a former military physician I can assure you this is not what they are interested in. They just want to find people with worrisome medical conditions that would prevent them from serving in a healthy capacity. Those are the ones they exclude, not the normal folks.