It's a little risky, if you're irregular, because you cant know for sure when your ovulation day is. It can happen right after your period or several days after that. It's hard to tell. And since sperm can live for up to 5 days inside the vagina, it's better to avoid sex during your period. You should see an obgyn about your long periods, girl! I'm sorry if it's probably not the answer you were expecting, but try to calm down and relax, get your mind off of it until you can take a pregnancy test or see a doctor. And get away from the internet! It's full of crazy stories that will only freak you out.