In Need of Advice from an Introvert's Mind

I, (20F), am more extroverted, and my bf, (21M) is very introverted, and needs alot of alone time. I am super understanding of this, and realize that we are different people, and he just needs time alone about 4x more than I do. But we have this cycle of him being super loving and thoughtful and affectionate when he's not stressed, but if he has anything on his plate, we only see each other say 7hrs a week.

We both love each other very much, and are serious enough to both want to get married after college, however, this cycle give me a lot of distress and after being very close for a while, and then all of a sudden getting nothing from him for days on end is unsettling for me. We've talked about this a few times but always settle on this is just how his brain works. Not only as my boyfriend but my best friend, I just want to spend more time with him, relaxed or fun. Should I be worried about this difference?

I also don't like feeling like he's always in control of how much time we have together, it feels like I always want to spend time with him, and he's always the one to cut the meeting off. we both initiate meetings tho.

Do you other introverts need lots of alone time even if you want to spend the rest of your life with someone?

How can I support him when he's stressed but wants alone time?

Should I be worried?

TLDR: Boyfriend and I are very loving unless he's stressed and needs alone time and the switch flipping from love to nothing for days makes me worried.