confused.. anyone else?!

so I have been ttc by using this app for the last 8 months, trying to track my period and when I’m ovulating and it’s always off. I always start my period like a week before it says I am and then when it says I’m ovulating I usually take an ovulation test and it’ll say negative so I’m not sure what I should be doing in order to find the accurate days. is this happening or has happened to anyone, what did you do? or any tips on how to figure it out easier.