Depo Question

Okay girls I’m 15 so I’m very new to all of this. Today had been exactly one month since I got my first depo shot and I have a few questions.

So i was supposed to start my period 10 days ago but the only thing I’ve noticed was a lot of discharge and some of it being dark blood.

Yesterday I had some blood for the first but then it went straight back to the dark stuff (but was heavier than before) and today I had nothing all day until just about 30 minutes ago dark blood again. Is this normal?

And my other question is, why is there blood and dark old blood if the shot is supposed to stop the eggs from being released?

This may be stupid questions but I’m just wondering because I’m new 😂😂