What went wrong

This the 1st time this app was incorrect, From my understanding you count the last day of your period til the day before the next start. I had a period Oct 24th according to the app I was due to have another one Nov 21 which would have made it 28 days the app said I was late 3 days so I’m my mind I’m thinking I could possibly be pregnant and it said it was cycle day32 why I am bleeding like a period I knew it was too good to be true I’m devastated this app has always been accurate for me. I just don’t understand 🥺😢💔💔💔💔💔💔💔💔💔💔💔💔💔💔💔💔💔💔