Clearblue OPK negative but...

Lena • happily married Yogi, Blogger, Artist...misssfaith.com
...when I take the test stick out I think I see a veeery faint second line - is it just me?
The last ones were really only one line. 
I'm turning into a slight psycho as I normally should have had a positive one already but everything was negative so far. Yesterday I felt completely sick with heartburn and period-like cramping although my AF isn't due yet. Last AF (first after my MC) started 4th of June.
Opinions?