I made an article where I talk about what you said.

Cogito, ergo sum — The meaning behind "I think; therefore, I exist"

For me, relativism is about the rest of the truths. I cannot be sure of the absolute existence of other people, of rules, patterns and everything studied by science, of anything I perceive, but I cannot deny that I perceive, or at least I think that I do, and therefore thought exists, and I have an abstract conception of myself, of self-identity (I identify as myself), so I exist, because "I" is just a word that denotes the abstract perception of the self as an individual, which is precisely what I perceive.

As I can only be certain of two things (existence of thought and myself as an abstraction of identity), such a strict definition of relativism where you can't be sure of even one truth isn't very adjusted to reality. If my philosophical views can't be called relativism, then I don't know any other name for them (relativistic solipsism or something like that, perhaps).