Originally Posted by WillYouStopDave
That's not a friend. Nobody needs "friends" like that.
I disagree about the above comment. Nobody is perfect, and friends do and say stupid and insensitive things sometimes. Especially guys. Guys like to bust each other's balls. There are multiple ways to handle this.
1. Tell your friend how this makes you feel... If your friend is anything like my friends when I was young, that will just add fuel to the fire.
2. Figure out what you friend is insecure about, and when he gives you crap about the size of your head, make a comment about his insecurity. If he gets defensive, then you can confront him about his comments. This would make him more likely to understand how you feel, and he'd have an incentive to quit insulting you if he believes it will stop you from commenting about his insecurity. This also has the potential to cause some animosity.
3. Punch him every time he says something about your head. Just kidding. However, if the above 2 methods don't work, confronting him aggressively is an option. If you choose this option, make it clear to him that you have told him how it makes you feel and that he needs to stop. You need to stand your ground if you take this approach and apply it every time he makes the comment. If he values your friendship, he should quit... or he will see it as a challenge to his male dominance and double down on it. Humans are stupid.
The more important thing is to deal with your insecurity. People very seldom judge other people by the size of their head. Yes, I am sure some people do subconsciously, but your are likely projecting your own self-judgment onto other people and your perception of their opinions. Your insecurity is also likely increased because of your friend. You are taking his opinion as fact and letting it influence your own beliefs.
It seems that you fear being judged as effeminate due to the size of your head. If that is the case, take steps to increase your masculine presence. Wear dark clothes. Maintain good posture. Be assertive. Obviously, that is easier said then done. You may want to research that topic. I know there are tons of Alpha-male/pick up artist books out there about increasing masculinity.
On a side note: While this won't help with the underlying insecurity, weight gain and long/fuller hair also increases the perception of the size of a person's head. Example, compare Leonardo DiCaprio in "The Revenant" to him in "Titanic". Sure there's an age difference, but the skull doesn't increase in size after the age of 23. He gained weight and grew longer fuller hair.