But that is the reality of open source. The very reason that all those BigCo’s are using your code is _because_ you offered it to them for free.
If you actually want payment for your code, but you’re not being up-front about it, then people are going to be annoyed with you when you show up asking for money, because they feel you’re pulling a “bait and switch” on them – because you kinda are.
The reality is that every one of us are relying on thousands of open source projects on a daily basis. Everything from glibc to our web browser itself are mostly if not completely open source. The number of open source projects involved in me writing this comment likely number in the thousands. I can’t practically support all of them directly.
Hard as it may be to hear, your open source project is not special. It’s just another among hundreds or thousands like it in the dependency stack. Only a tiny minority of the people who use it will even know it’s there, much less care that it exists. If you can’t accept that, you should probably get out of the open source business.