Honestly don't be too hung up on apps/day 14 etc. I've been pregnant 5 times (2 little kids and #3 on the way) and although I have very regular cycles, each time I got pg on different days of cycle. One time I got pg dtd just on cd 9 of 28 day cycle. Another I got smiley face on cd 11 and dtd cd12.
What I can also tell you is we tried for 7 months with our first - all supposedly perfect timing around cd 14 and it became so stressful. The 6th month I got totally fed, said feck it prob never going to happen and got pg!!
Each of the following pregnancies I never got hung up on it, just dtd after af finished for about a week. Best of luck xxx baby dust xxx