Do you have any idea at all when you ov Mandy? only reason i ask is that i have found that day 11-14 are a waste of time in my experience, i always get nothing at all! The last month my surge was late i didn't get a surge till day 17 but usually i get it around day 15.
With the internet cheapies i've tested twice a day, once at about 11am and the second at about 6pm. only problem is you have to pee in something and dip the stick, cant really do that out of the house lol!
as long as you test between 10am and 8pm you should be good, the reason i test twice is so i disn't miss the positive