'Uncertain' is a tricky term'. 'One is always uncertain about everything' - does this mean that 1+1 might not = 2 and that our existence might be a figment of imagination ? That these are logical possibilities about which you cannot have epistemological certainty ? By which I mean that you are uncertain that (say) 1 + 1 = 2 because you don't have evidence that gives indefeasible justification for the belief that 1 = 1 = 2.
So your examples are examples of epistemological uncertainty. But in your question, 'You are certain that you are uncertain?', while the 'uncertain' is epistemological, the 'certain' is subjective. It means that you have the highest degree of confidence that the beliefs listed in your examples, and all others like them, are such that you do not have evidence that gives indefeasible justification for them.
You might reply that you have not merely subjective certainty that you do not have evidence that gives indefeasible justification for the beliefs in question. Instead, you have epistemological certainty about this. But how so ? Ex hypothesi, this belief itself is not based on indefeasible evidence since there is no evidence you can trust. All evidence has gone with the beliefs which you have bracketed out as epistemologically uncertain. You are just left with the highest degree of confidence that none of your beliefs is based on indefeasible evidence. And this is merely a psychological, not an epistemological, state.
My suggestion is that there is an unintentional slide in your remarks from epistemological uncertainty to psychological certainty.
You pose an interesting question, intriguing to grapple with. Naturally I claim no epistemological certainty that I am right ! But you have my arguments.