the general answer to the question "did i have a breakthrough or not?" is "you just know".

But i understand where it comes from. The first time i had a breakthrough, i was wondering for a while if i had a breakthrough, or wether i had just died. You just don't know what to expect. Even breakthroughs come in different shapes and sizes.

I would say that if at some point during your experience, you're wondering if all of this is real, or whether it's maybe some very weird kind of dream, that's a strong indication that what you are having is a breakthrough or that you are on the verge of having one.