I assume you have a washer and the hose either came out of the drain or as was stated above, some of the drain hoses have come off under the bed. If it's the one under the bed, you have to take the mattress off to get to it as well as lifting the bed frame. As you slide your slide in and out this connection flexes. Once it's fixed correctly you won't have anymore problems.
SOB "The RV Wiseguy"