Implantation spotting?

The only time I’ve ever had spotting between periods were when my SO and I were BDing and it was too rough. My cycles are normally 30-34 days and my ovulation windows vary every cycle. This time, I spotted on cycle day 18 and have been taking OPKs. All were negative due to the fact that I started testing around day 17 (expecting my body to ovulate later in my cycle) so it can’t be ovulation spotting. Could it be that I ovulated earlier than expected and it is really implantation bleeding? PLEASE PLEASE let me know I’m so anxious and this is my first month TTC.

Update: I also have a slight sore throat got it the same day I spotted.