am I pregnant??

So New Years <a href="">Eve</a> I lost my virginity to my boyfriend. I have been on the depo shot for about a month and 2 weeks. When I got the depo shot for the first time I was supposed to start my period 2 days later but I never got one at all. I know the shot pretty much makes your period go away. Today (January 2) is when I should have started again. When we had sex we did not use a condom but all he did was pre cum in me just a little. Today it's only been 2 days since it happened but today I had a little of blood in my panties like I had started my period. I wiped and there was a little bit of light pink blood. A few hours later I used the bathroom again and it was just a tiny bit of blood. I am wandering if it is just my period and I have it this time because I didn't have the shot right before or could I be pregnant?? or did I pop my cherry??