Positive and negative pregnancy test?

Brianna

So, I took a pregnancy test from the dollar store this morning and the lines on the test were faint. But when I took a first response pregancy test a few days ago, it showed a stronger line. Has anyone had this experience before? Are my hcg levels getting lower? Please help, im worried I am having another miscarriage.

The bottom one is the dollar store brand?...what do you guys think?