Home pregnancy test Question

Ok, so I Took a test today, I have no idea when I ovulated as I just got off the Mirena on 6/28 and my body has been outta whack. So I took the test and I didn't see anything, a few hours later I came across the test again and saw a line. Is this a false positive since it sat? Or was my hcg too low to detect it right away when I first took it? I am going to retest in a few days, but was very curious. TIA  Baby Dust to all my Glow Friends✨✨✨😘