Have you tried ignoring the behavior? If it's because of the reaction he's getting then the function of the behavior is attention. Simply quit reacting /ignore the behavior. After a while he will figure out he's not going to get the reaction he's used to & he will quit doing it.

LOL, it would be very difficult to not react to that :-) I know how hard it is. My son bites for attention sometimes, but never my breast... I feel for you, ugh!!! Glad you are figuring out something that works.

Do you know how hard it is to NOT react to being pinched in the breast? I have used my reaction to redirect to tapping my wrist or hip. It has become less since then but still working on his behaviors. Thanks for all your help.

He has ABA, they tried a few things, nothing working. I think it's the reaction he gets.

Does your son get Occupational Therapy or ABA therapy? This seems like something one of those therapists could help you address.