Worried about another chemical pregnancy 😭

So I had my first VVFL last Friday so 6 days ago .. they kept getting slightly darker and then I had a BFP Monday and didn’t test again with a first response so I take a “$1 Test” from a gas station and I don’t know if the light line is due to it just sitting on the shelf for a long time or I’m not producing HCG like I’m suppose to. Suppose to start my period today , but had gotten positive tests at 9-11 DPO .. now day of expected period and got a light line on a cheapie test .. is it because they’re not as sensitive ?