OK the blue cross tests, are very well known for giving blue evap lines and or dye runs. They have the very narrow blue line to one side of the the thick line. just like in the googled picture you posted. These tests are not good to use, as they are misleading.
The Boots own brand is fairly good and sensitive, if that is negative, I would say that you can take that as a true reading currently.
Clear blue digitals are not that sensitive, and so would not show up an early result.
Regarding the internet cheapy tests, these tend to be prone to evaporation lines, so only read in the first 10 mins and discard.
Another word of warning, don't dip in the same pot or place a wet opk next to an hpt it will give a false positive on the hpt.
I think that if you are pregnant you are still testing way too early. Time to leave it at least a few days if possible and test again. If the positive opk was due to a secondary lh surge, then your period will arrive in the next couple of days.
If the positive opk on Monday was due to a late ovulation, then you could be waiting another couple of weeks for your period or positive test......
You need a little bit of patience with this right now.
Some women never get a positive test and have to wait a couple of months for confirmation of pregnancy..... try not to fret before your period is even due to arrive!!!!!
When you do test again don't use a blue dye, or digital test.
I hope you get a clear bfp soon.