What Causes Pelvic Pain With Heavy Bleeding And Clotting?

I am not sure if I need to see a doctor so would appreciate some advice please
I have had very light periods ( lasting 2 days) for the past 3 months. i did consider that I could be pregnant as I usually have periods lasting 6-8days. My last period was 15 days ago and lasted 2 days with minimal bleeding.
3 days ago I have severe pain in my pelvic area which lased a few hrs and was right sided. The pain subsided but my stomach swelled massively for the next 2 days ( I felt quite unwell with cold sweats , dizzzyness and sickness). Today I woke in the night with pelvic pain ( cramping/stabbing/dragging pain all over) and sudden very heavy bleeding. it is like someone turned a tap on and also huge blood clots are in the blood. I have been bleeding since with pain and also feel quite unwell.
Is this just a heavy period after not having normal periods for several months? Or should I see a doctor?