Maybe you need to explain more about your fatigue? How is this manifesting itself? What do you think is the relationship with caffeine?
Something I learned recently is that caffeine stays in your system for 12 hours. People who drink it later in the day often have trouble sleeping and get less sleep. Then, because they’re tired, they use caffeine to stay awake and it becomes a vicious cycle. So, if you don’t use caffeine, you don’t need caffeine—does that make sense?
I’d cut it out completely for a month, give yourself a 30 day challenge and monitor your sleeping and how you feel. There are lots of apps for that. Yes, the first couple day suck and you’ll probably get headaches, but then you won’t notice it. It’s only 30 days, what do you have to lose except possibly the thing that is concerning you?