What is the solution for dealing with forgetting the number of prostrations in prayer, which started happening a month ago?

The basic principle is that whoever doubts the number of prostrations should build upon the lesser number and complete the prayer, unless the doubts become frequent and turn into obsessive whispers (waswās). In that case, one must disregard them and pay no attention to them, because doing so leads to adding to the prayer despite being certain of its completion.