Skipping period

So I recently started the pill and just finished my first month of it, and I didn't take the sugar/inactive ones which start the period I guess, but for the past couple days I had like a brown discharge and I just thought maybe old blood or my body getting use to it. So I started a new sheet and went straight onto the white ones(my one has majority white pills and 7 red pills) but it changed from brown discharge to now like I'm on my period? It's quite light, but I am bleeding even though I didn't take the red one. Can anyone help explain? thanks :)