Hi, I Am 35 Years Old Single. I Usually Get

Hi, i am 35 years old single. i usually get my period on time or 1-2 days early or late but now is becoming more . on April & May 2016 i got it on the 15th but on June i got it on 19th still i thought its normal but now in July still i didn't get it ! it's already 25th !! i have travel planes which i made assuming that i will get my period on the 19th |!! when i called the pharmacy they advised me to take Promolute for 3-4 days 2 tab twice daily then stop it and then i shall get my period . please advise shall i start taking it ? i will be traveling on 29 july