Light spotting, late period, heavy bleeding, npt, ttc.

Robin
Hello Ladies! Let me start by giving a little history. I have two little ones, a 6 old princess and a 10 month old prince. I've been ttc since a gave birth to my son. My lmp was 9/19. On 10/5 I had pink/light red spotting that lasted for about two hours followed by fatigue, bloating, food cravings, headaches and mild presser in the lower abdomen (no pain what so ever). My cycle was supposed to start 10/15, 10/16 based on my normal 26/7 day cycle which makes me 3/4 days late. Hpt were negative. That appears to be normal for me as it happened with my other two. I had several neg test until I was around 5/6 weeks. On Wednesday 10/19 I started spotting followed by a heavier flow, I went to urgent care took a pt (neg of course), doc requested lab work and stated that If I'm pregnant that I may be having a miscarriage or ectopic pregnancy. All day yesterday I bled as if I was on my period (normal period blood color), no pain, no cramping, just a lot of blood with some clots and string like clots when I wipe. Today I'm still bleeding but it appear to be lighter with pin tip like clots. I'm still waiting to hear from the doct for my teat results. Any clue as to what could be going on? Am I miscarrying, is it a sign of twins, could I not be pregnant at all?