Birth control

Okay so I just started using birth control. I'm on my second pack. I am supposed to be on day three of my period, but the only thing I can see in my pad is clear discharge with the acational brown and red discharge. However it's never "blood". My reason I am asking is because I don't know what to expect and I am used to having an extremely painful period with a heavy flow. So this is weird and I'm worried it might be something other than birth control.