Coolant loss mystery

I have a strange problem: I keep having to refill my coolant and gradually (over a period of a week or two) I get a low coolant light and need to refill it. Yet I have no leaks, no nothing. Anyone have any ideas?

Check the lower rad hose, and the bypass hose. It is about 2 inchs long and you will hardly know it is leaking but check those two.