i too have trouble reading them sticks. had a digital last month made it easier, but couldnt get them this month. my lines nearly the same so im not sure if i detected it ?
There are several factors I see that could contribute to your result. Most women produce the LH in the morning/early afternoon, so that is why it is recommended that you test between 10am-8pm. Also some women have a short LH surge, so sometimes you need to test twice a day to catch it (AM and PM). The biggest thing I think contributed to your + followed by - is dilute sample though. You said you tested AM, got -, tested PM got + then waited only 2 hours to test again. You should restrict your fluid intake and "hold it" for at least 3 hours according to every kit I have in order to get enough of a concentration of LH in your urine for a good reading. It has also been found that the detection level of LH kits varies greatly because they are "cheaper" tests than hpts, so there is some variance in sensitivity. It is best to stick to 1 or 2 test times per day and make sure they are the same times each day, never use FMU and make sure you don't drink a lot of fluids or use the bathroom for 3 hours before each test time.
Yes, I've had problems because I am a shift worker and generally telecommute but I had to go into the office one day. I had to test at 10AM and 9PM rather than my usual 2PM and 7PM. I got 2 blank tests because I was outside the hours when I usually see my LH, but I couldn't do anything about it because we have multi stall bathrooms at work and I couldn't sit for 10 minutes in a stall to baby sit a pee stick. Then I tried a bunch of test times because my wake time ranges from 7AM-3PM and finally just set an alarm at 11am so I can get good temp and OPK results without losing so much sleep they are skewed. Closing the range helped quite a bit.
You may have caught the surge on its way back down. Let's say the surge started sometime overnight, and you caught it this afternoon, and by the time you tested again, it was back down. If so, it sounds like you BD'd at the right time...but I would also BD tomorrow and the day after...just in case.
Another explanation could be that your urine was not as concentrated when you tested the second time. Had it been 3-4 hours since your last test (or since last time you peed)? And did you limit your drinking before testing?
That's why I buy digital OPK's. It's a circle if it's negative and a smiley face if it's positive. It saves all the questions..more expensive though.