even for normal healthy fertile couples, it can easily take a year or so to fall pregnant, sometimes longer (tho obviously some couples get lucky within weeks of trying). how long you leave it before consulting a doctor would probably depend on your age and history. ie if you're in your mid 30s you may wish to find out as soon as possible if there are any fertility issues, but in your early 20s you may nto feelt eh same urgency. Ditto if you or your current partner have children from a previous relationship, but have not yet conceived together. My partner and I had planned to try for a year or so, then see how we felt about getting medical advice. luckily enough, we fell pregnant about 9 or 10 months into that year. Good luck.