Hi, I Hope You Can Help Me. My Menstrual Cycle

Hi, I hope you can help me. My menstrual cycle started about 15 days late. Now that it's here I've been experiencing abdominal pains majorly on the left side, lower back pains on the same side and also clotting like no other. Can you please tell me what these could be possible signs of or whether it's a normal occurrence.?Thank you so much for listening.