“My period is late?”

I took one pack of Minigynon 30 contraceptive - perfect use, i.e. the exact same time every day for 3 weeks not having a late or missed pill. I had unprotected sex on day 6 of the pill as well as day 21 on the last pill. He ejaculated in me at all times. I didn't take any other pill or anything from I took the last pill. I had light bleeding and spotting lasting 4-5 days starting the 4th day in that break week which I presume was my withdrawal bleeding. I didn't start another pack or have sex after that. My cycle is usually 30days sometimes less as I am 11months postpartum. Now my cycle is 5-6days late. Could I be pregnant? I've taken one pack of birth control years ago and my period came back at the usual time then. Is it normal to be this late after only one pill pack or could I be pregnant? I got most of the pregnancy symptoms but I guess they could be PMS though I never really had much PMS before.