I Missed a pill ...I think

So I noticed last Monday that Id forgotten to take a pill. ..so I thought. So I immediately doubled up the following morning. Later on in the day I noticed that a pill was missing from the pack from the following week, but I couldn't remember if I took it or if maybe it simply popped out in my purse. I've been taking my pills everyday normally. Should I start a new pack? Also should I be worried about pregnancy?