Trying for baby #2....

I have PCOS( very mild)... I'm trying for baby 2, I've been using an app which has been following my periods. My average period lately has been 33 days and according to this app I should be ovulating in 2 days. Do you find these apps being accurate? I got an ovulation kit and start using it a bit late in my cycle. It was my first time using one and might not have understood it; I think I ovulated about a week ago (2 days after having sex)... I'm only on day 17 of my cycle and was cramping/bloated really bad today for about 3/4 hours, is it possible that an egg has implanted??