sometimes you can get a lot of clots if you have a build up of old lining in your uterus, I wouldn't panic but share the info with your doctor, in case it continues

Hiya Hun, they put me on BC too and the same thing happened to me I now refuse to take them due to the bad large clotting I had. Plus I believe they can mess with your cycles/stop your periods and the period you have while on BC is not a real period! It's a withdrawal bleed or what they call a fake period! Research it xx

Hello, welcome to the site, my name is Robin... and in answer to your question, really bad cramps and blood clots, this might help: https://www.verywellhealth.com/why-are-there-bl...(Phone number can only be seen by the question and answer creators)

"Causes

Depending on your age and your medical history, any number of factors could be pumping up the volume of your menstrual flow and/or causing bigger-than-average clots to form, including:
1. Uterine fibroids, which are noncancerous growths in your uterus and very common.
2. Endometriosis, a condition in which the endometrial tissue in the lining of your uterus grows outside your uterus, usually onto your fallopian tubes and ovaries.
3. Adenomyosis, a condition in which the endometrial tissue in the lining of your uterus breaks through and begins to grow in your uterine wall, often making your uterus larger.
4. Hormonal imbalances, including hypothyroidism, polycystic ovary syndrome (PCOS), perimenopause, and menopause, can cause your menstrual cycles to be irregular, which may result in clotting and heavy bleeding from the uterine lining not being shed regularly.
5. Miscarriage, which can happen very early, before you even know you're pregnant, and result in clotting and bleeding.
6. Cancer in your uterus or cervix, though this is unlikely."

I don't have a lot of blood clots that I remember from my last 4 or 5 periods, but I do know that I had some bad cramps.