help, should we try a first response test instead of these dollar store tests?

We've spent more than $100's of dollars on hpt and decided this month to get $1 tests and a vvvvfl keeps coming up. Is it really positive???? It was like this yesterday maybe even a tad bit lighter. Either 1 week to af or according to Glow I start Wednesday. 
Today 1/15/17
Yesterday 1/14/17