I Am 45 Years Old And Am Having A Regular

I am 45 years old and am having a regular period from the start but last october 2022 , my period did not come until december 2022 . My ob gyne advised me to take duphaston and i started to take the medicine last december 23, 2022. On the 5th day , december 27 , i already got my heavy period and it lasted until january 1, 2023. My husband want to have sex with me but we want it to be safe. In this case, when will be my safe period. My husband just arrived after six months of duty and will be leaving again on January 8. Am I on the safe period now and if so, until when? My worry is that i got my period this time because of duphaston and not because it is really my regular cycle. Thank you.