I'm sorry you've been trying without success. That being said, your OPK is not positive until the test line is AS dark or darker than the control line. The light line you saw does not indicate anything other than the fact that there is some LH in your system at this time - but many women always have some amount of LH in their system at any given time.
In regards to you ovulating on Thursday, may I ask how you came to that conclusion? If you are using a period or fertility calendar/tracker/etc, that is likely not accurate. I would advise you to click on the ticker in my siggy, which will take you to Fertility Friend. You can read the tutorials and learn how to chart your cycles. I highly recommend you consider charting your basal body temperature so that you can confirm you are ovulating.
I also recommend that you read the newbie link at the top of the page - it is full of great information.
Welcome and good luck!