Well I've had the same problem for years with my cycle. Do you have problems with your cycle being irregular? Because sometimes the lining in your uterus can build up(that's what peels away and sheds during your cycle) and come out in small clots. You should go to your gynecologist just to make sure you don't have any ovarian cysts or any other underlying problems that would contribute to you having blood clots. Especially if they're painful or abnormally large, I would definitely schedule an appointment ASAP.
