Spotting instead of period with uterus spasms

Hey,

So on Friday I woke to what I thought was my period, not a heavy bleed. Saturday it was gone, then had very light spotting yesterday and today. Now my uterus is doing full spasms, like somersaults haha!

I’m nervous bc my period is extremely regular+never ever off! Lasts 3-4 days full bleeding. I’ve also never felt these spasms. Negative pregnancy test yesterday.

Does anyone have any idea what this can be!?

Seeing my obgyn tomorrow.

Thank you!!