What is this?

I had unprotected sex 10 days ago.could this be implantation bleeding? Btw I'm not due for my period by a long shot so Ik that's not what it is..when should I take a test? I was thinking Friday. ( and the spotting is brown, Idk if you can tell from the picture) ( annnndddd I'm on birth control and he did cum in me and I didn't go to the bathroom right away because I had to walk back home) (it's the birth control shot) and I have been slight cramping throughout the day but not like period cramps .have been having bad headaches and terrible mood swings? I'm going to test Friday . And also I have only had two shots in total, got my last one on July. And ik sometimes the shot makes you bleed but I'm not supposed to until October so ik it's not that either but I've always been the odd one out on a lot of things health related also. Should I go get blood work?