If you have a 28 day regular cycle then you would ovulated around day 14 counting from the start of you period to the start of your next period sperm can survive in the vagina for around 5 days waiting for the egg to be released so anywhere from day 10 to day 15 the chances would be at there highest, once the egg gets released it then has around 24 hours to be fertilized before it dies and the chances of pregnancy drop. Seeing as you have irregular periods it would be harder to say exactly when ovulation will take place.
Another method to know when your ovulating is to study your discharge when your ovulating it will be clear like egg white compared to the opaque colour the rest of the time, the other way is to go by the feel and position of your cervix. If you Google signs of ovulation you should find all the things you need to know.
Hi, I'm 15 years old and my boyfriend and I had sex earlier today. It was unprotected and he came on my tummy. I'm not sure if I can, but can I get pregnant if he wiped the cum off himself and waited a minute before putting it back in? My mother will kill me if she finds out and I'm trying my best to get answers. I usually get my period at the beginning of the month, so most likely it will be in a few days. I want to know if I am pregnant, but if I get my period soon, does that make it negative? I'm just very afraid, I've never had in protected sex before, I'm always safe but this time I screwed up and I am worried. Any ideas?