I would test with the same test you took two days ago and look for progression of the line. Normal tests often aren't positive until you've actually missed your period
You are using different tests which can range from 5iu to 25iu. If it’s 25iu at 12dpo it’s unlikely to show up x
I would only stick to the early ones which are like 10imu for the first week as your still early and tests that where 25imu (standard) tests are used for around and after you period is due ,the first week I only used 6/5 days early tests as that will show progress better ...🤞🧡
Test with a red dye , if not sounds like a chemical ,,