I've been having irregular periods and just recently had unprotected sex where the guy came inside me and want to know if there was a chance I might of got pregnant?

Yes, there's a chance. Even if you had "protected" sex, there's a chance. Any time you have sex there's a chance.

Of course there is a chance you are pregnant, you took a HUGE risk if you are not looking for a child. Use protection if you want to lower the risk of getting pregnant.