Check Coolant Message....

[justwaiting]

I was driving back from Ft Lauderdale to Tampa yesterday and noticed a message "Check Coolant Level". I parked the car and went into Costco...did some shopping and bought some coolant...came back to my car and opened the hood....and noticed my coolant was low....I didn't see any residue or ruptured hoses...I then added coolant..and drove home(another 1 hour). I got up this morning and started up the X5...only to get another "Check Coolant Message"....I opened the hood...took a look and the level was low again...I must have a leak...Any recommendations on where to look? I'm going to make an appointment with my dealer if I get the message one more time....I have a jug of coolant in the car...and the temperature is not above normal on the engine...