wondering if I can adjust the app...

hi ladies!! so this month I did my opk's( I only had 2 left and I'm pretty regular so this is what happened) the 3rd I got a negative opk. the 7th I got a high (just figured peak would be around the next day) now I usually get my period any time from the 20th-23rd. never earlier and never later. Well this month I got it on the 17th...which seems like only about 9dpo?? I was so excited because I thought it was implantation bleeding, but it seems too heavy. now I changed my period day to the 17th in here and it then shifted my peak week back a week saying one of my highest days was the 3rd..now I know that's obvs wrong!! I want to be able to adjust my ovulation week on here but idk how. also why in the world did my period come so early???!!