I bought a weeping cherry tree 4 or 5 years ago with a 3 or 4 inch trunk diameter that was maybe 10 feet tall. Now the trunk is 6 or 7 and it is about 15 feet tall or more. It has lost its shape and seems out of control.
What is the best way to get it back in shape and under control?

It's not really possible to answer the question without seeing the tree. By out of control do you mean it has non-weeping branches, or just grown too big but still weeping? If you could please post a picture we would be able to assess what could be done.

Yes, a picture would be helpful. I'm thinking some judicious pruning is in order. I know most of the ones around my city could use it. They look great if pruned properly.