Possible miscarriage?

Christina
Hi everyone, I woke up at around 8:30 this morning, I had bled a lot through the night and obviously thought AF was here, my periods are very irregular since been on the pill, so thought nothing of it, now during the day the bleeding has gone much much heavier, I'm passing a lot of clots and I've had excruciating pain in my lower stomach (which is very unusual for me as my period is usually quite light and I never cramp), I've had to change my tampon 3 times in the space of two hours and I'm leaking a lot too. I'm very worried as I haven't had any pregnancy symptoms and I'm still taking my pill.. I've tried a hot water bottle and nothing eased the pain, it's calmed down now but keeps coming and going...
Could I be miscarrying? I've rung 111 and they have a doctor ringing back within 2 hours.. Any advice would be good.