Adult size plastic pants are available that will let you sleep through the night with out wetting your mattress. Google will help you find what you are wanting.

I wear them and sleep knowing I may wake up wet, but my mattress is dry.

Plastic pants and a vinyl sheet is what I use. 

There are vinyl mattress pads. Plus the various disposable incontinence pads (chux pads).  What is Your level of incontinence ?  Do You wear a pad or brief (diaper)   All these questions can help answer Your question.  

Darlene Stephan - If you are leaking through an incontinence pad into your mattress, you may need to invest in new pads or use two at once.

1. Maybe you need to move up from moderate protection to heavy protection. The "Specifics" section of the descriptions will tell you how absorbent a model is as will the customer service division of the retailers.

2. Are these pads that you have used for a while? The pads are designed to withstand numerous industrial washings, but they will eventually deteriorate and must be replaced when that happens.