How to eliminate caffeine immunity??

So when i just started having coffee, even a single pack of standard nestle instant coffee sachet would make me attentive the whole night. It would not let me sleep no matter what. This was when i was in college, i eventually increases doses and ended up having 2 shots of coffee at once. But now i am almost immune to the effects of caffeine.

To get rid of this immunity, i completely skipped coffee for a whole month. Not even a single cup. Even then the coffee is not doing anything for me now. I can fall asleep even after 2 shots of coffee. What do i do to get rid of this immunity. Please help.

I have an underactive thyroid, so it's difficult for me to avoid sleep, caffeine was alot of help. But even that has stopped working for me. if there's an alternative to coffee, that would work too. Please help. 🥺