J.L.
Hi! I tolally sympathize with you! I breast fed both of my children. One was a thumb sucker and one was not, but, I felt like a human pacifier with the one that did not!
My ten year old only stopped sucking her thumb when she was 8 1/2. I tried EVERYTHING! I could think of. Old folk remedies...wrapping the thumb, my sis tried hot sauce (That one upset me) the stuff they sell in the store, etc. But, nothing worked. Finally, my niece got her to stop when they went on vacation together. She is a wee bit older and told my daughter that people were looking at her sucking her thumb, and she might not make friends if other kids saw her doing it . It was embarassing at times.
To my relief, her teeth are fine. But, regardless of what I tried, and I tried since she was a wee one, it took someone her own age to finally convince her.
I've been told that they should not be forced to stop because they need the sucking action for soothing themselves, and until they learn how to sooth themselves in some other way, let them alone.
I hope this helps in some way. It's not the worse thing that they can do!! lol