Since Saturday, I've had very faint lines on 4 different brands of tests. I don't believe they are indents as I dipped 2 brands in water and no second line showed up. All my lines look like the picture below. I got a positive opk on 5/5 and my cm dried up like normal to indicate I ovulated (normal for me). I'm still getting positive opks!

I've had mild cramping (which feels different from period cramps) for a week, backache, nausea, no appetite, food aversion and fatigue. Anyone else experience this? Why am I getting these lines and not pregnant?