period clots?

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hi I’m wondering if anyone of you could offer some advice, lately I’ve been having excruciating lower back pains and stomach cramps. I never normally get blood clots like this in my period and I’m wondering if anyone could help? my period started off with brown/pink discharge and spotting and is now a dark reddish brown colour. I also have a very irregular period could that have something to do with it? I am sexually active and have a few pregnancy scares but im just wondering if anyone has any advice? I’m thinking of going to the doctors later on today, thankyou! (The clots are jun roughly the size of a 10p coin and is quite thick and fleshy looking in person) x