Hi Doctor, I Had My Menstruation On 24th Sept For

Hi Doctor,

I had my menstruation on 24th Sept for 5 days. I had unprotected sex on the night right after i finished my menstruation. I took postinor 2 on the next day. 5 days later i had 2nd menstruation for 4 days and had unprotected sex again on the 5th day. I took postinor 2 again on the next day and had 3rd menstruation for 2 days after 4 days taking it (the blood is just like few drops). These means I already have 3 times menstruation in 1 month. Should i take postinor 2 again if I have another unprotected sex after the 3rd menstruation? will it be effective? Will my ovary producing ovum after having menstruation 3 times in a month?

I do heard that postinor 2 should not be taken more than twice in one month. Can you tell me why it is not safe?