Female question about PMS and big blood clots.?

I first want to say that I'm going to be going to a gyno next week. Pardon me if this grossest anyone out. I have always had an abnormal period ever since I started. I always got cold sweats, puked, and severe cramps that kept me out of school. Not just your normal pop an advil and it'll go away it was real bad. Well for a few years (mid 20's through early 30s,) I didn't have a period. No pain no nothing didn't think anything was wrong b/c my sisnlaw didnt have a period. The past three months I started getting a period on the 11th day. My family thought it was b/c of stress due to my mother in the hospital. It came again this month but the blood clots were huge. As big as my hand. Once again no pain. I thought it was due to the fact I didn't have one. (Like I said Im going to the dr on Monday). I was just wondering if anyone had an issue like this. Im now feeling a little bit of lower back pain. Any advice would be greatful :) I have looked on Google and it all says the same thing. thanks in advance.