I had unprotected sex the day of ovulation saturday at 3am and i took the plan b pill monday at 6pm is that 72 hours? and could i still get pregnant

In time, probably.: Of course, the sooner plan B is used the better, but it can help even up to 5 days later. HOWEVER, it is not 100% effective. Do a pg test in 3 weeks. Get checked for std's if you have had unprotected sex, unless in a mutually monogamous long-term relationship (& you were both disease free before beginning it). Practice safe sex to avoid both pg and disease going forward. Plan B is no substitute.