How Safe Is To Avoid Contraceptives On Having Irregular Periods?

Hi, I have been diagnosed with PCOS since I was 18.Currently my age is 23.I rarely menstruate, I mean i menstruate around every 5-6 months.So after having unprotected sex with my partner do i need to have an ECP (Emergency Contraceptive pill) or is it like I am at no risk zone without having ECP even.Would really appreciate if anyone here could guide me through.