Tested Positive, but Worried...

I tested positive twice on Saturday and have tested every day since. My tests this morning aren’t at all darker than yesterday (they’re actually lighter)and I’m worried that something could be wrong. I was 18 weeks pregnant in October when I found out I miscarried my husband’s and my daughter. When I was pregnant with her, my tests got progressively darker for the 6-8 weeks. Could any of you please give me some insight? I’ve included photos of all of the tests I’ve taken so far.

P.S. I have my first doctor’s appointment on January 3rd, when I should be about 6 weeks pregnant.