how long so you have to wait before the doctor will start doing tests in case something is wrong?
Usually 12 months, unless there is a reason why you think something might be wrong (e.g. I was seen after 6 months because I was having 100 day cycles and temperature charting clearly showed that I wasn't ovulating). To most GP's, not falling pregnant wouldn't be a reason to be seen sooner, because it can take up to 12 months for normal, healthy, fertile couples to fall pregnant.

I know the waiting is frustrating though

You can have a CD21 blood test that will indicate whether you have ovulated or not - it tests the level of progesterone in your blood. That, or pregnancy, would be the only foolproof way to guarantee that you were ovulating, but all the other signs are quite reliable indicators, particularly in combination