Had anyone had hpt tests that don't get darker?

Hey girls. I am feeling insecure and emotional because every day that I take a hpt since I got my initial bfp, I get a line, but it had never been bold and dark and it hasn't gotten darker from first test to last. Has anyone else experienced this and had no issues? The Internet has so many horror stories that I feel like I'm freaking out about a CP or MC and I have never been pregnant before and have no reason to worry. Any positive stories would be really helpful. Thanks!