Help please I'm confused!!

So I've been having a friends with benefits fling with this boy and everything has been going great, 
I went on the depo shot so we could be having sex safely 
Everything has been fine but my period is about 14 days late n I assumed it is because of the depo shot but today I got a little blood twice but the first time it was brown n the second it was super light & very red and I'm not sure if I'm spotting due to the depo shot or because I'm
Starting my period or early signs of pregnancy...? 
I haven't been having any period or pregnancy symptoms but I need to know if it's my period or the depo shot? Or should I be worried about pregnancy
I need to know fast, I'm supposed to see him tomorrow... 
Please n thank you! 
Can I still have sex even if I'm spotting or is that not good?