Spotting when your period should be??

I am almost 17 weeks now and every month I still bleed when I get close to when my period should be. I’ll get similar symptoms too and I can feel it coming; cramping and even worse fatigue and more. Anyone else have experience with this?

I have had ultrasounds to check on baby and they all say everything is okay but last month was pretty decent bleeding and a couple small clots. They still say everything is fine.

I just don’t understand why this is happening? I haven’t found any medical explanation to ease my worry. People say spotting happens but I thought that by now it would have settled down.