This solution is not Minecraft specific; it uses the external tool "Auto Hotkey" to emulate clicks
For any auto-clicking, or any keyboard emulation behaviour - I'd recommend looking at AutoHotkey (AHK).
This is a 3rd party program for Windows, which allows you to emulate any number of keyboards and mice, and programmatically control them. Due to it's prevelance, most tasks you wish to accomplish have already been solved and shared online.
There is a usage guide on their official site, for how to install AHK and how to create the auto-clicking scripts you need: https://autohotkey.com/docs/Tutorial.htm
Please note, as with any 3rd party software - usage is at your own risk.
For the autoclicking script itself, here is a simple example:
toggle = 0
Toggle := !Toggle
The effect is, once the key "F8" is pressed; AHK will begin looping the Click action. Once the F8 key is pressed again, the value of "Toggle" is reset, and the loop ends. It allows you to turn on and off the clicking. There are of course, much more complex auto-clicking techniques you can employ using AHK.
Using online tutorials and searching, I'm sure you will be able to tailor this to your needs. Otherwise, specific AHK scripting questions can be answered on StackOverflow.SE