Weird Period this month

I am on Antibiotics for a UTI. I was supposed to begin my period today BUT I started spotting yesterday. Today I am still spotting, it’s barely noticeable. Like only when I wipe I see it. I have a medium flow so this is very abnormal for me.

This also happens to be the first month that my husband and I are TTC. He came out for the first time 1.5 week ago so I don’t know if this could possibly be implantation bleeding? Or could it just be the antibiotics that are making it super light?