Period!

Hey ladies! So I used the depo shot for not quite a year and I skipped my shot for February because we wanted to start trying for baby #2! I know that it can take quite some time to regulate your period and body and getting pregnant immediately isn’t likely! So we weren’t expecting much. So I have started having regular periods, but I’m August I had a normal period and then maybe a week after it ended I started bleeding again but this one is much worse, it makes me nauseous, my stomach feels yucky, my back is hurting and I have a regular headache, but it’s not the normal period blood it is extremely dark so I thought oh it’s just old blood coming out at first but it’s just like a period, so I’m just a little confused.. Why am I bleeding again? And why is it so dark? Does it mean something? Is this part of my body “regulating” anyone else experience such?