I have a male GSD pup who is 5.5 month old now.  He rarely messes in his crate as i regularly come back home and have to clean his cage up.  The problem is, is that when i go to open his cage he starts to wee, but not just a little bit, he seems to let it all go.  In fact he does it whenever me or anyone come close to him.  This is becoming a problem as i feel i can't take him anywhere.

This problem seems to have gotten worse in the last few months.

Please help

"He rarely messes in his crate as I regularly come back home and have to clean his cage up."   

How long are you leaving him in the cage for?  He is either very exited to see you or absolutely bursting to go.  Or being very submissive - does he get into trouble for doing it?

If it has gotten worse in the last few months presumably he's always done it?  Have you made sure there isn't a medical cause?