Unless you are over 35 I wouldn't suggest you see your doctor until after 12 months. It's considered perfectly normal to take around 12 months to conceive. Many pregnancy books say it's about a 20% chance each month (and your chances don't increase each month, it's still the same) so you just have to keep at it til you hit the jackpot.

I've been through 2 lots of investigations for fertility problems and I would only recommend it after you've really given nature a good chance to take it's course. It can put a lot of pressure on you (emotional & financial) and your partner. Nothing was ever found wrong with me medically (apart from a so called fibroid that's never been seen in any of my pregnancy scans) and I ended up conceiving without any assistance.

Eat healthy, cut out caffeine (mind you I conceived this bub whilst having huge amounts of caffeine), eliminate transfats from your diet and take folic acid.