Blood clots

When your on your period does anyone get blood clots? Something isn't quite right and I'm going to the doctors this week because I've had my period for almost 3 weeks now and I've been having a lot of blood clots come out when I wipe. And I mean A LOT. It's not normal. I can't be. Honestly I'm scared and want to cry my eyes out. I'm just like what if something's wrong and I have cancer or I can't have kids?