We're sorry to hear you are eperiencing nighttime leaks. Size and fit are a huge part of finding the right diaper for your baby. As you know, babies come in all different shapes and sizes so diapers fit every baby differently. Our diaper sizes are organized by weight, and since no two babies are the same shape you will notice some overlap between sizes. We're happy to assist you. Please give us a call at 1-833-646-5262 for assistance.