Positive lines are getting less visible?

It’s been 3 days and each day I’ve taken tests and the pos line has been getting lighter with each test. The first day it was there, clear as day. Yesterday it was so light but we could still tell it was there. But now this morning it’s barely there at all. Could this mean I’m miscarrying? I’m only about 3 and a half weeks along so it’s still very early. Just wondering why the pos line would be barely visible after being so dark just a couple of days ago.