Yes, i am facing this problem when my son is 15 months - 19 months. Every time let him wear diapers and clothes will make me crazy.
The end i bring him to see doctor and do a diagnosis. my son is a autistic boy. So got behaviour problem.
But for your case, i think your boy is normal but only behaviour problem. you can try ABA training. This will help us train our son behaviour. A lot of normal kids will go to ABA training too