An agnostic doesn’t believe it’s possible to know if god exists. A gnostic thinks it’s possible.
Agnosticism is about knowing, atheism about beleiving. So if you don’t know if god exists but firmly believe the idea is a load of crap you’re an agnostic and an atheist.
Friend of mine hadn’t ever seen a newborn baby before she gave birth. She was quite shocked when her newborn daughter “looked like an old man”