Trying to get pregnant 🤔

So... third round of trying to get pregnant. I’ve been tracking periods with this app and trying to track ovulation and fertile days but still keep missing.

I’ve had 3 children (boys) and got pregnant the first try with no problem . Now trying one more time for a girl and... nothing. Anyone have any advice? Before I head to a doctor. Trying to be patient but it’s stressing me out now.

Am I now too old (31) did my eggs shrivel up dry lol wth is going on?!!