Not all women ovulate in the middle of their cycle. So, unless you're using on ovulation predictor there's really not an absolute way to tell when you ovulate. Can I ask why you would have unprotected sex with some guy? Are you trying to get pregnant at 16 years old? How can you be sure he does'nt have any STD's? You can't. I recommend using a condom every single time with every single sex act. STD's and especially babies are no joke. All you can do right now is wait for your period. Some of the really good ones may tell you if your pregnant or not a few days before your period is due.
Oh and I had unprotected sex and the guy I did it with said he might have cummed in me