Home pregnancy test confusion

courty625

I had two clearly positive home tests a few days ago, no faint lines, both were pretty visible with the left line being slightly darker. I took another one this afternoon ( because this is my first and I'm paranoid it's going to "go away") & the left line was WAY darker, the right you could barely see. Does anyone know which line is the control line & what this could mean? I'm trying not to stress but I'm worried my levels are possibly going down.