You can ovulate late so or even twice in a cycle (although twice is rare) so . . there is no safe time to have sex in a cycle. However, it takes a bit for pregnancy to actually happen after the unprotected sex. It's not instantaneous. in about 2 to 2.5 weeks, you can get a positive pregnancy test from the date in which you had the unprotected sex. We can be late due to things like illness, stress, changes in routine, weight gain or loss or just a blip in hormonal radar. Try not to worry. Timing sounds off for pregnancy but since you still had a slight risk, see what happens with your period and test in 2.5 weeks. good luck