Hi there. Well, a bit of time has passed. What's the latest? In general, you can get pregnant if you have unprotected intercourse at any time during your cycle. Some times are less likely, but not totally safe. If you are saying you had sex and the next day your period started, the issue is that you don't really know if it is your period or spotting. But in general, I'd say that is a LESS likely time for most women. Periods can be late for a variety of reasons including stress, changes in routine, illness, just a blip of hormones.