There is always the possibility of pregnancy with unprotected sex. No Birth Control method is 100% guaranteed, and pre-cum can contain sperm. Other medication as well as sickness can interfere with BC pills. However the risk seems low.
Periods can come late. Ovulating late means a late period. So you may just have a late period. Stress can cause period delay.
If your period doesn't come in a couple of days, try a DIY pregnancy test.
Hope this helps