Hi Bethany,
Because the LH takes approx 4 hours from when it is released into the blood stream until you can detect it in your urine you need to leave approx 4-6 hours between testing. My ob suggested I test at 2pm and at 8pm. When I did this I detected a second line at 2pm - approx 2 shades lighter than the control and at 8pm the line was gone altogether. Another cycle I tested with only a very feint second line at 2pm and by 8pm it was 2 shades lighter than the control. So, you see if I had only tested once a day then I would never have detected that surge. One of those cycles I requested a s.progesterone test and it showed clearly that I had ovulated. The other cycle I conceived so I obviously did ovulate! So, my body is a case in point that often the surge is not detected by a 'true positive' as outlined in the instructions. Had I waited to BD until I saw a 'positive' second line than I would never have conceived! I did actually use Fortel for a while and I did receive a very very feint second line on two cycles. When I called the company they told me I should purchase another pack of tests as my surge was probably on the way. Five tests later and I had no more second lines! That is when I began having my serum progesterone done. Each blood test showed a very healthy ovulation had occured - my progesterone was above 20 on each testing.
It does seem excessive to test twice daily and it is expensive. However it may just help you to catch your surge as it did for me... Without twice daily testing I wouldn't have picked up what was happening. It is totally a personal choice. If you had charted your cycle and you knew approx when you ovulated then you would only need to test twice a day for say 3 days before your expected ovulation which is what I did. I have tested twice daily this month from day 8ish as I miscarried last month and wanted to know when ovulation occured... For me this month I 'appeared' to get two surges. However in retrospect I think my body 'geared' up to surge on day 13 but I believe I actually did surge on day 19-20 as the lines were darker then - time will tell that story! Have a look at a website entitled peeonastick click on the opk odyssey and it will show a series of opk's and what they looked like. The author of this website is a firm believer that the test line has to be darker than or equal to the colour of the control line to be positive - I know that for me that is not so!

To answer how often do I get a second line? Using Lullaby I only ever get a second line just prior to my two shades lighter than positive result. So, often one test say at 2pm it will show a light second line and then the next test it will be darker. I do sometimes get a lead up day where I will get a very, very dust: feint second line and then the next days testing the line is darker and then by the 8pm testing it is darker again and then the next day at 2pm the tests go back to a clear stick with no second line at all. You will find with Lullaby that you need to wait for about 7 - 10 minutes until all of the background colour on the test strip disappears. Then read your test.
Get that blood test done, you could even do it tomorrow or Friday and then you will have an idea. Make sure you tell the doctor that your cycles are 33 days (I think that is what you said, sorry if I am not right) and you want to know if you are ovulating.
Well, I have felt pregnant since about day 21, so I am not sure what the go is. I have had the odd glass of champagne over Christmas, because my tests late last week were BFP. I am still using my opk's and I have registered a second line that is getting darker each day from cd 28. So, who knows. A BFP would be a beautiful gift at this time of year.
Lots of love and baby dust to you. dust:
Keep me posted!
Deb