What Causes Heavy Bleeding In Menstruation?

I ran out of Cerazette pill about 3-4 weeks ago so I missed 3-5 days before I started back on the pack I m on now. I ve been taking it again for 17 days now. 3 days ago I started to bleed heavily following painful cramps, & I m still bleeding heavily. I never had a period on Cerazette save for the first few months over 1 year ago when I first started taking it again following a few months break and while it settled down. Previous to that when on this pill for a few years I never had periods. The last time I had sex was 1 May so about 8 weeks ago. I m using tampons but I m a bit worried i shouldn t in case I m miscarrying - is this possible? Should I go to my GP or GUM clinic when the bleeding stops to check me? I m worried it might be miscarriage because I had a few weird symptoms prior such as very swollen ankles. I ve also got a very bad cough at the moment & I am sweating badly at night but assumed this is due to the virus making me cough. However it s difficult to tell what is related to the bleeding if anything. Eg my muscles ache & my breasts feel tender & I my sense of smell is strong. Thank you