I Took A Prenancy Test About A Week Ago It

I took a prenancy test about a week ago it was positive.... but this morning i woke up and i had light pink spotting... later on that day is started bleeding bright red with blood clots.... i just had my son 9months ago and every cycle i had since then been heavy with blood clots.... i wont to know should i be concerned ... this never happened to me.... this is my 4th pregnancy.... should i be worried...what should i do.... im scared im having a miscarriage.... any opinions