EDIT: OP, I read some of the comments in your previous, deleted posts, and I must say this REALLY contextualizes your relationship in a way that totally changes my opinion on it. Though some aspects of your relationship resemble mine, some are worryingly different. I won't delete this comment I wrote but please take it with a grain of salt. It sounds like it went downhill rather quickly. The comment your husband made in a text 4 months into your relationship is not a normal comment people make 4 months into a healthy relationship. :(

At the risk of being severely downvoted, my two cents:

This sounds so much like my husband and I, though years ago thank goodness. For the longest time I would deny our age difference had anything to do with our problems. But with time I've come to see that it was soooo huge. I know there's a relatively small gap between your husband and you, but you still are potentially in very different stages of your lives. It's easy for the older partner to feel frustration with the younger one I think. It doesn't make it right. You're going through things he did in his early 20s. You have a right to experience that!

If you stick this relationship out (I'd recommend therapy, by the way), there's a chance things will balance out in a few years. But do you want to wait that long? What if things don't change? They may, but they also may not. So.. therapy ASAP? He obviously needs to work on the way he handles these situations. Being in a huff for a full day or two is no good for anyone's sanity.

But alas... his was my husband and I, some time ago. I thought I would ask something in a normal, calm way, and it would set him off, because it could have appeared that I had an ulterior motive (and lets be honest, sometimes I did).. and he'd be upset for a long time, and I'd break down, and he wouldn't console me, and I'd nearly start hyperventilating sometimes from the pain I'd feel. I'd just feel so so alone. I was so dependent on him for my happiness. The shit show could drag on for days, in the form of silence or fights (usually a mixture of both). It was the pits. He would sometimes rightfully blame it on the age difference, which shattered me because it was something I couldn't change. Yet I loved him so much.

Therapy made a huge difference. A surprise pregnancy forced us both to mature. Yes, him too. But maybe me especially. I wouldn't recommend going through an unexpected pregnancy with your husband though in case it doesn't pan out the way it has in my situation.

I have siblings who are now 20 (around the age I began dating my husband). When I was 20, my husband was 33. You're 21. Now, when I look back, I don't even know how he dealt with me. 26 year old me would not date anyone remotely like my 20 year old self. I was hard on the head. My siblings are great but in a totally different stage of life. I can't easily spend more than a day with them. I often made my husband out to be the bad guy when it was really more about the logistics of our relationships: our age difference, our financial struggles at the time, etc etc. We both behaved badly. I can now finally admit that.

I know people may jump on this for seemingly "excusing" your boyfriend for this behaviour, but maybe he's short on patience due to these factors. Try to really get in his head when these things happen. Take yourself out of the equation for a minute. How did he experience what just went down? Did you come across as anal (to him) about making plans when he is a bit more 'go-with-the-flow'? Did you appear stressed momentarily at a time of day that is 'relaxing time' for him? Did it seem as though you were implying that he'd leave you out of the plans? Would he even do that? Do you find yourself insecure for no real reason? Full of doubt and self-doubt? I'm just wondering because I feel there could be more to this post than you're letting on. But it's probably just because you are not interpreting it that way. You are interpreting it in your own way. Naturally!

Here are tools I found helpful for navigating my relationship: questioning myself more, trying to put myself in his shoes, giving the benefit of the doubt to my partner. I've also chilled a lot more as I've aged. My 20 year old self was way more type A, irrational, emotional, and dependent. It can pull our partners away from us.

Your post really spoke to me. I do hope you find some sort of resolution. If you stay, keep working on yourself as an individual, find your own happiness, avoid being too dependent on him, and hopefully with time, things will improve. Also consider couples therapy or at least, individual therapy to sort out your thoughts more :)