This follows on from the previous question.
If you are both under 35 and have been trying to conceive for a year or more then see your doctor.
If you are 35 or over then seek your doctor after 6 months.
There is nothing to stop you seeing your GP if you have been trying for less than a year but the medical professions define infertility as failure to conceive within a year.
Your GP will talk things through with you before referring you for fertility tests.