as previous posted said, AF won't come until you O. If you tested for O earlier in your cycle and it hadn't happened yet, AF will be late. The only way to know if/when you ovulate is to chart your BBT. Opks can help indicate an LH surge, but just because an opk is positive, it doesn't mean that you will ovulate. Some women have multiple LH surges every month before successful ovulation. If you are new to TTC and are having irregular (or potentially anovulatory) cycles, I would highly recommend that you start charting your temps. That will help you identify your pre-O symptoms and confirm ovulation.
http://www.fertilityfriend.com is a free charting app that many here use. You can pay for an "advanced" version that includes some extras.
For temping, you'll want to use a digital thermometer. One that registers to the 100th of a degree is recommended over the ons that just register to the 10th of a degree (although I used the regular digitals and had no problem). Take your temp at the same time every morning, after at least 4hrs of uninterrupted sleep, and BEFORE you get out of bed. You might want to set an alarm for say 30min before you normally wake up to ensure a similar temping time every day. General rule of thumb is that 3+ days of raised temps relative to the previous 5-6d temps indicate that Ovulation happened on the last day of low temps. You can go to the charting section to see some examples of charts.
Remember that a chart won't tell you if you are pregnant. It will just give you information about each cycle: it can identify pre-O and pre-BFP symptoms, will tell you if/when you ovulated, and will tell you how long your cycle (total, and LP phase length) is. Typically, the LP (time between O and arrival of AF on a non-BFP cycle) will be 11-15d long. If you consistently have very long cycles, or cycles with an LP less than 10d, you might want to talk to your doctor.
GL