LH surge?? Please read

Joanne
Hi, I usually ovulate on day 15 or 16 according to bbt chartig over the past 3 months. This month I decided to use ovulation predictor kit and got a positive test on day 12! Do you think this is a false positive? I'm so confused! Am I ovulating early??! I have been sick with a cold for the past two weeks- could that make me ovulate early??!