Edit: I probably should have mentioned but I am level 2 autism so apologies if anything isn't clear. I am mentioning it because it affects my communication and understanding of others, not to excuse any bad behaviour.
Since I (21NB) was a child I have always been incredibly averse to any facial hair, specifically beards and mustaches. I am not sure where it comes from, and it's not applicable to any other body hair (including armpits, genitals, or hair in other areas). I never had an issue with any other body hair on partners, only facial hair. The thought of being intimate with anyone that has facial hair, even my own boyfriend (22M), is really off-putting and makes me very uncomfortable. It sounds stupid and I've tried getting over it, but it's been this way since I was a child and I don't think it will change. I also can't imagine kissing anyone with facial hair, thinking it will feel weird and "ruin" the moment as it will touch my face and potentially sting me. I am not judging anyone who has it, and I have friends who do, this is specific to my physical and sexual attraction even though I know it sounds stupid.
Recently my boyfriend of about 5 years has wanted to start growing his facial hair. Since we've been together he has always shaved it and in the past never showed interest in growing it out until recently. At first when he told me (about three weeks ago), he thought I was joking around when I mentioned I did not like it, and mentioned disliking it since I was a child. At the same time, I did not tell him he had to shave it off, because he wanted to try it as he said it made him feel confident / good about himself. I was completely fine with him growing it, but couldn't get over the discomfort of imagining being intimate when he had facial hair. So he had started growing it out and it was more than it had ever been.
Last night he brought up that he wanted to grow it out thicker and longer than it currently was, and I couldn't help but feel completely nauseous at the thought. That is when I told him directly that he is 100% allowed to grow it out, and as much as I support his choice, it will affect my physical and sexual attraction to him. He was very hurt, and I tried explaining to him that I would still be romantically and emotionally attracted to him, that it's not personal, and I know it sounds stupid but I cannot help feeling so uncomfortable with it and don't think I would be able to handle intimacy. I also said he should still grow it out if he wanted to as he said it would boost his confidence and shouldn't let my preferences / feelings / discomfort dictate his bodily autonomy. I felt awful after seeing how hurt he was. He is a really amazing person and boyfriend. At the same time I did not want to stay quiet about it because what if in the future he notices me slowly withdrawing from him as a result of the facial hair?
Today he told me he will shave it off and that he doesn't want to talk about it and doesn't want me to mention the situation again. He said he was very hurt to hear my words, and last night to him felt like I was giving an ultimatum and that I'd basically let something as silly as a mustache affect our relationship. I felt so horrible after seeing his hurt reaction even though I tried explaining to him it wasn't an ultimatum and he could still do it. And maybe I will get over it, but as of now I was very uncomfortable with it. He said that it was an ultimatum to him no matter how I was wording it, which I can understand why it felt that way. It wasn't my intention but I understand the impact was different.
He pretty much settled with shaving it when he was looking forward to trying it out. When I asked him similar scenarios like if he would also be attracted to me with facial hair, he said yes and that it wouldn't matter to him as it was still me, which made me feel even shittier. We haven't had a proper conversation since, and he doesn't want to talk about it and asked me to respect his decision to not bring it up again. Not wanting to talk about it is completely fine and I respect it, but I do not think the situation is resolved until we talk about it properly. I asked if there's anything I can do for him in return, if he wanted me to change anything about my appearance but he said there wasn't. I asked if he wanted to see a counsellor together about the situation but he did not respond.
My aversion again is just specific to facial hair, including on myself. Any other body hair is fine. If he were to gain/lose weight or get tattoos and anything else I'd also support it as I love him for more than that. I can't tell if it's some sort of phobia or psychological thing against facial hair and told him I'd be willing to try getting over it but cannot guarantee that I will. It sounds so stupid when I am attracted to everything else about him (his personality, his looks, him as a person) but the mere thought of facial hair overwhelms me with discomfort to the point where I feel disgusted / grossed out, and it basically destroys my physical / sexual attraction completely.
Did I mess up? I will be speaking to my therapist about it next week. As of now I feel horrible but don't know what I could have done differently. Any advice on what I can do for him moving forward would be appreciated. For now I won't be bringing it up as that's what he requested from me.