Hi Springtime,
I would guess it is probably best to wait until say 14 or 15 days after ovulation at the earliest? If you're not monitoring ovulation then it's difficult to say. The safest things is to wait until your period is actually due (or hopefully late!). If you test before then and get a negative you may just find you tested too early and can't rely on the answer. You can get a false negative with the tests if there is not enough HCG in your system yet, but a false positive is rare (if not impossible?).
So the danger of testing too early is that you just don't believe the answer if it isn't positive!
I think the test that advertises the earliest testing is the First Response Early Response and that says you can test up to 6 days before your period is due. However, if you test that early it only has a fairly low percentage of correctly identified positive results (ie still gives a lot of false negatives). I forget the percentages off the top of my head.
The other thing about testing early, even if you do get a positive result is that you could still have a chemical pregnancy (which is like a really early miscarriage - before early testing people would have just thought it was their period arrived on time as normal) so depends if you'd rather know about that or not.
Incidentally, there is no reason why you should be monitoring ovulation at this early stage in ttc - it adds more pressure than is necessary unless you suspect there is a problem.
Anyway, apologies, that has turned into rather a lengthy post - hope it's not too rambling and makes a bit of sense.
If I've not been clear - please say so and I can try again :)
Oh and good luck - hope you get a positive result nice and quickly.