You said some people booked their holiday after receiving your invitation and you are hurt by that. The trouble is, and what you don’t seem to realise, is that when they book, they may have little choice about whether it clashes with your birthday or not. Because holiday dates are notoriously difficult to sort out, with all the factors involved, they may only have been able to have those dates, or miss their holiday altogether. Surely you wouldn’t have wanted them to do that?
If it had been, say, your wedding, then maybe you would have a reason to be upset and hurt, but for a birthday? I have just had my 80th and would have been devastated if anyone had thought they ought to miss their holiday because of it.
So yes, I think you are being very unreasonable.