Could it be implantation bleeding?

I came for my vacation trip to Dominican Republic to see my husband. I’ve being here since December 16. Since then we haven’t use any kind of protection, ( I have PCOS) so, I don’t worry about getting pregnant that easy. But, today something happened; I bleed first thing in the morning during sex, it was just a little bit of blood. For a second I thought I got my period (which I haven’t had in 8 months) but then I didn’t bleed for the rest of the day.

I have no cramps or any signs of getting my period. So, my question is, is it too early to tell if I got pregnant and that was implantation bleeding? Or what could it be?

Also yesterday I was a little bit dizzy and nauseous.