Period bleeding has strange breaks?

Hi, I'm 18 years old and I've had a really strange period rhythm for a while now. I usually have a lot of pain and a lot of blood for the first two days and then everything is fine again, but recently (I'd say since January) I've been having heavy bleeding for 2-3 days and then I have a break of 1-2 days where no blood leaves my body before it starts again with a kind of spotting for 2-3 days and excruciating pain. After I spoke to my boyfriend's mum, she said she's really worried and that I should see a gynaecologist. Unfortunately it's a Wednesday and no doctors are open, so out of curiosity I wanted to ask what it could be and whether anyone has had a similar experience?
It might also be important to say that I have been taking the mini pill (Swingo30) since I was 15, but so far I have had no problems with it.
Please only helpful answers, I know that you should go to a doctor with this but as I said no one is open and before the conversation I wasn't really aware of how serious it could be.