My boyfriend has small dick syndrome

Hello everyone, I want to share my boyfriends story so maybe you can help him understand that he is completely fine! When he was about 11 years old he was obese, once he was at a gathering at a friends house and they were talking about dick sizes and wanted to see my boyfriends dick, so they pulled his pants down and started laughing because they couldn’t see it, the fat was covering most of his penis, since that moment until today 11 years later he still dealing with this insecurity about his dick, I have to say we measured it 100 times and it always says 18 cm or 7 inches and 11 cm or 4.3 girth! I find that to be very big but he can’t see it that way no matter how much I tell him or how much we investigate or measure him, he still sees it as small! Can you please give me any advice that might help him understand what he has and appreciate it, I want him to be comfortable and happy like I am with his body! Thank you in advance! ✨