Draw?

It ended in a draw because you did not leave your opponent a legal move to make. Your opponent only has a king and he would be in check no matter what square he tried to move in. Such a situation is ruled as a draw and "stalemate tricks" are a valid strategy for salvaging a lost game.
In order to avoid this in the future, always make sure to either check your opponent or leave him a move. It also helps to go for the quickest mate instead of wasting time capturing their last few pieces or promoting all of your pawns. Having such overwhelming force makes stalemates like this one far more likely.