so I have been using OPKs for this first time this month and yesterday I got 2 lines that almost matched in colour it only needed a little way to go, anyway the next morning I tested expecting it to be a blazing positive but it was an obvious negative, womanlog maps out my ovulation date for me and ovulation was forcast for yesterday, we BD'ed twice I had negative OPKs before that day so now I dont know if I had a dodgy test or if my LH surge was just really short.... if it is really short does that mean i wont ovulate or something else??
Don't worry about a short LH surge. Some women get positive OPKs for days and others (like me) only get it on one day. Mine is very quick and difficult to catch. Sometimes I can only catch it because the line is dark one day, and then the next afternoon it's lighter (and I calculate "damn, ok I must've surged 2 days ago then").
Try to take it in the afternoon because many women surge in the AM, but it doesn't show up in the urine until the afternoon, so taking it in the AM on the day you surge, you'll miss it, then taking it the next day, it won't look like a positive.
Your body only has one LH surge, so if the lines were getting darker, then suddenly they're getting lighter, you can be pretty certain you surged.
Then of course, assume you'll ovulate 24-48 hours after you think the LH surge happened.
Good luck!
ETA: Well, I don't want to mislead anybody. It is possible for a woman to get multiple LH surges (but it's kinda rare), and also possible for a woman to ovulate twice during one cycle. So either or none of these might have happened to you ladies on this thread who mentioned having almost positive looking OPKs then later had a more definitive LH surge.