Hi there. Unprotected sex is always a bit of a worry for unplanned pregnancies and std's. I don't know what our cycle is like or what day the 26 was in your cycle or when your period is/was due. If you are late, you need to take a test. The way a cycle works is the first day of your last period is cycle day one. And you count from there. Most women ovulate midway through their cycle but sperm can live for about a week. But it is hard to say with the little info you've given. If you are late, take a test. good luck