Vvfl not getting stronger?

Dye • EDD: 9/26/19 💗🎀 Geriatric pregnancy 😂 Second pregnancy although it feels brand new! 16 year old son 💪🏻💙

I took a test 9DPO and got a vvfl. Took another 2 days later, same thing. Took another this morning, same thing. AF is due tomorrow. Is this normal or could it be a chemical?