Is early startup CTO burnout unavoidable?

I've been CTO at a pre-seed software startup now going on 4 months. Actually, things are pretty great: we have several paying customers who like our product, we're not spending time on anything other than getting us to PMF, I like my coworkers very much on a personal level, our business doesn't sell guns to kids or isn't a dopamine factory, so I'm doing something I can sleep at night about.

However. I find that even doing the "core" part of our business requires a lot of heads down coding time from me. Even just writing basic "business logic" software day in and day out. Customer wants a new integration? I have to hop on that ASAP. Customer wants to use their dashboard in a different way? I have to hop on that ASAP. Even just keeping with what's needed for customers is just almost overwhelming for me. Not from a technical perspective - from a technical perspective this is all trivial CRUD logic. Easy peasy. But just the sheer amount of it is mind numbing. I find my days - day in, day out - are just this mush of heads down code work from sun up to sun down. It sucks. Every time I get to the point where I'm like "ok, and THIS is the last thing we're doing for now", something changes, or I have to go back and refactor something based on new info from a customer.

Oh boy can I feel the burnout coming. We don't plan to try to raise for another few months (we want to raise on our terms and by that point we should have a strong customer base). So my question is, is this just life as an early-stage CTO? Just writing code all day, every day until my mind is numb? Is there any way to mitigate this? Again, we have several customers, things feel like they're going great! But as the only software engineer at the company _everything_ tech is (rightfully) on my shoulders and I think the sheer amount of work I have is removing what "fun" I might be having in the job. Am I just being a crybaby? Thanks