If one is always in doubt as to which Rakaat of Salaah they are in, what do they do?

If one experiences doubts during Salaah regularly regarding the number of Rakaats of Salaah performed, then one must apply their honest discretion and act on it accordingly.

For example, if after applying one’s discretion as to whether they are in the 1st or 2nd Rakaat of Salaah and one is more inclined to be in the 2nd Rakaat of Salaah, then one must take it as they are in the 2nd Rakaat of Salaah and complete the Salaah as normal.

However, if one has no inclination as to whether they are in the 1st or 2nd Rakaat of Salaah, then one must follow the lesser of the two Rakaats of Salaah and take it as they are in the 1st Rakaat of Salaah.

In this case, one must sit for Tashahhud after performing every Rakaat of Salaah and perform Sajdah Sahw at the end before completing the Salaah. (Maraaqil Falaah 1/183)

And Allah Ta’ala Knows Best