ovulation confusion

Hi moms and moms to be... i have few doubts about when exactly i ovulate. we have been TTC from past 3 months. the app i aas using to track ovulation was giving me incorrect data and we just wasted 3 months...😥😥😥 so do we ovulate on 12 the day or it changes as per your cycl1 length?

so my last period is 30th jan i bleed for 3 days.. so i will be ovulating by 10th feb or by 16 th feb?? please help... iam using 3 different apps and also tracking my symptoms.