Please see a doctor to find out whether there's anything going wrong inside your body. Protect the bedding by using a waterproof mattress cover and/or a bedpad. An absorbent towel can do wonders when strategically placed, and another can cover any wet areas in the morning. Diapers are good, too, but can become expensive. I'd first try to find out what's wrong, then decide whether this is a short term or a long term problem. If long term, please consider a good quality absorbent diaper, cloth or disposable, for nighttime use. A weak bladder isn't the end of the world, and your daughters are likely used to wearing protection themselves during critical times of the month. They will understand, and you might take a bit of ribbing, but any embarrassment you feel is left over from potty training days. Accidents and wearing protection are not babyish; hiding your problems and pretending they don't happen both are.