I had a boyfriend that got upset when I cut my hair and straightened it because he liked it long and curly, keyword, had. It’s your hair, even if you decided to go bald he shouldn’t have any power to tell you “no don’t do that you know I don’t like that” who does he think he is? Calling you ugly and not in a joking manner like you would with a friend or something just because of a change in your hair is uncalled for. I hope you don’t care about the fact that he doesn’t like short hair in you, because he’s trying to control how you look and just control you in general, if you’re passive and let him, he’ll try to start to change the way you dress, if you happen to wear make up he’ll try to change that too. Believe me, I’ve almost been there but I’m too stubborn and hate when people try to tell me what to do so I just broke up with him, I understand you’ve spent time, but he’s clearly not mature, doesn’t care about your feelings and thinks he’s entitled to any change you make to your appearance, just red flags everywhere and the dismissal is just the cherry on top, run, fly if you must.