help a girl out!!!!

So I am on the pill and my period was last week but the past couple of days I've had what feels like period cramps and a dark browny coloured discharge.. I've had this a couple of days before my period before but never after, I'm also usually quite consistent with taking the pill but yesterday I did forget because of how busy I was but took it as soon as I remembered, could that be the reason or is there something else going on? I'm going on holidays tomorrow and I don't want this interfering! Please help a girl out!