Could Spotting Post Unprotected Sex Be Implantation Bleeding?

Hi, I was administered my first Depo Provera shot last June, on the 7th. I didn t have a period the entire three months until a week before I was due for my next shot. Due to a mix-up at my doctor s office and them not calling in the script, I never ended up taking a second one. According to my fertility tracker, September 11 was (roughly) my ovulation day. Naturally, on that same day (before I consulted the fertility tracker), my boyfriend and I had unprotected sex and unfortunately took no precautions. Now, three days later, I m spotting and it s very similar to the spotting I experienced when I had our first child. I m aware that it could be mid-cycle ovulation spotting, since implantation spotting usually doesn t occur as soon as three days later, but we have also had sex many times before the 11th. And seeing as the 11th is a rough estimate for my ovulation day (I couldn t quite remember when the end date of my period was but it was either the 5th or 3rd or 4th.), then it could be possible that the spotting is due to implantation; so, since my period came before the second Depo shot was due could possibly mean that I was capable of ovulating already? I m aware that it can be quite a while before women get their periods back and therefore ovulate, and after that it could taken even longer to actually become pregnant, but since I received my period before the shot was due and my boyfriend and I had sex even before my ovulation day (assuming I was actually ovulating), is it possible that I could become pregnant? That the spotting I m experiencing could be implantation spotting or mid-cycle spotting? Or is it basically impossible that I could be pregnant? Basically, I m just wondering if it possible that, coupled with the immediate return of my period and the spotting several days after intercourse (whether mid-cycle or implantation), could this mean that I am fertile and therefore possibly pregnant?