M.B.
Some kids are just more orally fixated, and may stay that way unfortunately. I have 3 kids, and one of them to this day puts things in her mouth that I just don't understand and she's 7! She certainly "knows" what shouldn't go in her mouth, but she does it without even thinking about it a lot of times. She has gotten better, but like I said, I think some kids just have an oral thing. She never sucked her thumb, but used a paci for way longer than my other kids and breaking that habit was very difficult. It's been over 3 years, and I'll still catch her making sucking motions when she sleeps sometimes. Try to be patient and encourage other soothing activities. Good luck!