HOW DO I TELL MY BOYFRIEND HE SMELLS??

HELP!!! Me and my boyfriend will have been dating for about 4 years in April. I am a very neat and clean person, but he on the other hand is not. He grew up in an abusive household with constant trash laying around and was never encouraged to shower, brush his teeth, or wash his clothes ever since he was a child. He moved out at 16 but still carries these bad habits with him at 20 years old. He is a bigger guy (around 260 lbs) so he sweats often and will come over after work with smelly clothes and the smell is unbearable. I can’t even touch him or go near him because of this awful smell. I have mentioned it to him before and he tells me he will try to keep up on it and not be around me when he is smelly. It has gotten so bad to the point that his smell will linger on his chair for hours after he leaves and I will have to febreeze/wash wherever he was sitting. It’s gotten so bad and I don’t know what to do without upsetting him. PLEASE HELP!!