Can i become pregnant since i had sex on fertile day ?

Of course: This is the rhythm method for timing of the ovulatory and sexual cycle. You had sex on the highest time of fertility so it certainly is possible that you might have a pregnancy as an outcome.

Well, yes of course!: Especially if you did not use any protection. You might incidentally have several fertile days each month, depends on the survival of sperm in your system. If you don't want to get pregnant, you know what to do!