Faint Positive?

Hi guys I'm new to this but am always reading these chats to see what's being said and for advice. I was wondering if someone could tell me why I had a faint positive line on a ClearBlue test in the morning and when I tried a digital ClearBlue the morning after I got 'not pregnant'. Ive bought 2 more normal tests to do in the morning and see what they come back with. 

I hace PCOS and have really irregular periods, but as I'm trying for a baby I'm always testing, but I've never once seen a faint line on a test, just the line to say I'm not pregnant. 

Heres the photo of the test. Anyone else had something like this before?