Help?!

Ok so I'm really new to all off this. Me and mu partner has had unprotected sex.. Waited a few weeks and I done a superdrug test few days ago.. The first test I done it showed me the test has worked but on the box where is shows if you are pregnant or not a faint pink horizontal line appeared almost straight away and faded after 5 mins or So. This has confused me as if I was positive surely it would be a vertical line and it wouldn't disappear Or could it be a evaporation line? So when I got home I did the other test as it came with two and it came back at negative and no line appeared whatsoever?? And surely if it was an evaporation line it would happen on the second test? ADVICE???