18/19/20 DPO - line check?

Hey guys!

I’ve been worried about my line progression. My pregmates just aren’t getting dark .. and I’m around 18/19/20 DPO. I tried other brands today to compare and they are much darker. What are your thoughts? I also have had a stiff neck all day.. worried about ectopic .. I called my obgyn to ask about my neck. She said she doesn’t think it’s ectopic because I have no other symptoms. She recommended I take Tylenol.. I did and it’s like 80% better. What are your thoughts ?