I'm 15 dpo. I thought I could be pg this cycle, began bleeding today. Theres no flow to it. Red brown pink mixed with cm. Only see it when I wipe deep?

Pregnancy test. Some light bleeding or spotting can be normal in early pregnancy. Check a home pregnancy test.
Hmmm . . . ? Let's see. You're a 15 year old female on depo-provera for contraception. If you've been getting your shots every quarter as directed, it's very unlikely that you're pregnant (assuming that you've had otherwise unprotected sex - which you shouldn't do b/c depo only prevents pregnancy, not sexually transmitted infections). More likely, you're experiencing spotting commonly seen w/depo.