Could I be pregnant while I'm still having regular monthly periods?

Breanna
Me and my guy have unprotected sex pretty regularly. I am on the pill (the one where you still get a regular period once a month). Since I take my pill every night around ten, sometimes I'm just exhausted from the day and fall asleep before then so I forget to take it. Normally when that happens, I just double up my pills the next night. It doesn't happen a lot, but it does happen. However, my last period was a little weird. I had to double up pills two nights in a row because I just had an exhausting week and kept falling asleep before I remembered to take my pill. During my period week, nothing but old blood was coming out and it was a very light flow the entire week. Only once or twice I saw new blood when I went to change a tampon or a pad. Is that normal for people that have pill mishaps as well or is there something wrong with me? Please comment.