Pregnancy test query

Red • TTC 10 months
Ok... So I bought a very cheap tescos pregnancy test at first both nothing then both windows showed a positive line then the main window (yeh or any window) started to fade... After 1 min it faded to almost nothing and after 2 it was gone...
​Now I'm going with do another non cheap one... Or take it as a negative and treat as a temporary false positive ..
​Advice please? 
​Or do I do the normal wait and see if AF pops in :-)