Don't ever trust an "app" to tell you ANYTHING! They are notorious for being unreliable.
No woman ovulates for 6 days. Ovulation takes place in the blink of an eye, on ONE day only, when a woman releases a mature egg. She is fertile for about 2 days before and 2 days after that one day, for a total of only 5 days each month.
From what you wrote, I'm not sure if you know what your "cycle" is. Your "cycle" each month is comprised of the days between the first day of your menstrual period, and the first day of your next period. It begins on the first day of your period, and it ends on the first day of your next period.
If he "busted" on your butt area and some of it got on your shirt and on your underwear, it's almost impossible that you could get pregnant. In the first place, your "butt area" is nowhere near your internal reproduction organs. Secondly, sperm cells could not penetrate the fabric of your shirt and your underwear, and somehow find their way into your vagina.
I'm not saying that you aren't pregnant; I'm saying that it's unlikely that your are (at least not this time).