my BFP too much of a BFP?

Savannah
This is dumb (new mommy, I'm sorry!) but it's been on my mind a lot lately. When I took my first test, my line was DARK DARK. Glow said I was about 4.5 weeks along at that time. Was I just very pregnant? I've been told dark lines are signs of birth defects and nothing scares me more than that. Should I worry?