Any success stories of really light pregnancy tests?

Looking for some comfort right now because my mind is reeling. I'm 5 months postpartum, and my period, which just started back in December, is late this month. Now I thought it was just that its all wacky because of breastfeeding hormones, but I decided to take a FRER test and it had a super duper faint line. I kind of freaked, but thought that maybe it was an evap. I checked yesterday, a slightly stronger pink line appeared, but still very light. I check again today, same thing, but maybe even slightly darker? I thought I was about 17 days dpo, but with my last pregnancy, I was about 14 dpo and my FRER test was super dark. Is every pregnancy different? Can a faint line mean something is wrong? Maybe it's too early to tell, but I definitely do see a line. Perhaps I ovulated later than I thought. Any successful pregnancies come out of having faint test lines? I would be happy if this is a successful pregnancy, just didn't think it would be so soon.