What is entailed upon me if I swore multiple times regarding the same matter, with the expiation changing each time, then I broke my oath and forgot the last expiation? Do I owe one expiation or multiple expiations?

According to the Hanbalis, the statement "If I do such-and-such, then I will do such-and-such" made by way of obligation is considered a vow of "lajaj and ghadab" (obstinacy and anger). This is when a vow is conditioned on something with the intention of preventing or encouraging an action. The Hanbalis give the vow-maker the choice, if the condition is met, between fulfilling it or offering an expiation for an oath (kaffarat yameen), based on the hadith: "There is no vow in anger, and its expiation is the expiation of an oath." If vows are repeated, one expiation suffices. It is advisable not to make vows, but to strive to fulfill what is remembered of the vowed actions while also offering an expiation for an oath.