My son replaced one undesirable behavior with another

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He is almost 6 and it took forever to get him off the pacifier. His OT said it was part of his sensory thing. I stopped providing it and he eventually forgot about it....or so I thought. It has been nearly 8 months since he has had one and I have noticed a few months ago that when I woke him up he had the neck of his pajama shirt in his mouth, it was soaking wet. His teacher at school brought to my attention that he is now doing it in school. He gets his sleeves so wet that they have to roll his sleeves up and sometimes change his shirt. How do I change this behavior or help him to stop without replacing his need to suck.?