Ident or positive? Confused

So ladies if you could help me understand this I would greatly appreciate it!

I took this test and several others since Wednesday (because I was suppose to start Wednesday) and what happens is the line is there and clear as day when time is up (as far as waiting to look at the results) but then the longer it sits the line becomes lighter very hard to see and almost disappears. Can anyone explain what's going on?

The first picture I circled the line (because I was sending it to my husband) the second picture is what it looks like 10-15 minutes after reading results.