Ttc short cycle

Hello I was wondering if anyone is in the same boat.

I have a period tracker which also tracks my ovulation but the problem is my period is shorter every month and it will not let me edit it so I can get an accurate read of my ovulation. My cycle is about 20 days and the lowest the app will go is 24.

Also with a 20 day cycle is it harder to conceive?

My dr said everything was fine in blood work when my periods started to come closer and closer together about 9 months ago. But I’ve been ttc for 5 months and nothing so far.

Any advice?