Short period 😩

So i took plan b on july 10, 30 minutes after the mishap. Glow said my ovulation day was july 9. Before the tenth, i didnt engage in intercourse none of my fertile days. Well i got my supposedly period on the day it was scheduled. I bleed heavy for 2 days then on day 3 and 4 little to no flow. Im normally on 5 days. Should i still take a pregnancy test? Could it have been implantation bleeding?