I've had pre-conception tests which include hormone levels, iron, folate, vit d levels, immunity levels, cmv exposure etc. It wouldn't hurt to get these done through your GP. Then if there's a concern, getting a referral to an FS.

The 6/12 month thing is a guideline based on the average couple, most of whom wouldnt know when ovulation occurs. There's no reason not to investigate earlier if you're concerned.