An ammeter has a resistance of less than 0.1 ohm so basically the result is the same as shorting the output of the regulator.
The ammeter should be use in conjunction with a load, for example you use a 5 ohm resistor with a 5v regulator (the resistor in series with the ammeter) and you read the current that flows through the load.
What kind of supply are you making?
If it is a constant voltage supply then the current will change according to the load, for example 5v /5 ohm 1Amp , 5v/ 10 ohm 0.5v , if you connect a load that needs 5v 1A then that is the current that the regulator will provide , it will not force high current in a load that "requests" a lower current.
If you are trying to make a constant current source then the regulator changes the output voltage in order to keep the current of the load constant and in the set rating.
So which type did you make?
Are you trying to make a constant current source for the led?