Not understanding the app.

Nicole • 27 Years Old TTC #2 for 7 months.
So I started my period on Feb 6th and doctor told me, and every website I have checked, says I "should" be most fertile around the 18-22nd of Feb. Been having a lot of issues with my period so my doctor wants to make sure I'm ovulating so I will be taking ovulation tests this month. But this app is telling me I'm most fertile starting the 11th of March..... Doesn't make sense to me. This will be the first time I have tried to track my ovulation with kits so I'll just start testing early I guess so I can pin point this month if I'm ovulating or not. Ugh why can't this just be easy?!? :(