I thought I started my period now I’m not sure

Thought I started my period out tampon in as normal went on with my day. I have had weird feel like I’m having a spasm in my Uterus but it’s on and off. I took my tampon out after 5 hours each and there wasn’t even enough blood to cover the tampon. It’s been like that for two days and now I’m not bleeding at all! I have never had a period like this before.

I did have implantation bleeding with my son and thought I started my period do remember having bright red and pick blood but that was just a one time thing since this time I have been bleeding on and off for two days could it still be implantation bleeding this time ???