When to worry

So, my husband and I have been TTC for 7 months now. I'm 31, he is 33. I was really hoping to have a baby before 32, but that's almost impossible at this point (unless I get pregnant this month). My periods have been somewhat irregular (30 - 40 days). I know they say a year is the cutoff for infertility, but is there any reason for that number? As far as I can see from data I've read, 90-some % of couples are pregnant in 6 months. If that's the case, when should I get worried? (Bc I already am a little worried)