Is it necessary to fulfill a vow to fast two consecutive months upon interrupting prayer, given that the number of times the vow was made cannot be recalled?

Praise be to Allah who has cured you of whispers (waswas). Vowing to fast for two consecutive months if you stop praying is a vow of obstinacy (nadhr al-lajaj), in which the vower has the choice between fulfilling the vow or offering an expiation for an oath.