Just late or pregnant??

So last week me and my SO had sex and he came inside me so a couple of hours later we went to the clinic and got the morning after pill. I was meant to come on the day after but now I'm 6 days late which is completely abnormal for me. I'm meant to take a pregnancy test in a couple of weeks but I'm wondering, is it more likely that I'm just late maybe as a side affect of the pill or am I more likely pregnant. Just need a bit of advice???