Indent or BFP? Help!

Brandy
I took this test mid-day, after work. I'm on cycle day 37, which means I'm about 5-6 days late. 
Immediately after taking it, I saw something faint. At the 5 minute mark, there was nothing. At the 10 minute mark, I could clearly see a thick, faint line. 
I'm confused. I'm testing again in the morning but I'm just wondering if anyone else has had similar experiences.