Do LH strips show if your pregnant???

su

I tested a few days back and got a BFN and I used my last one at 10 DPO. And don’t think I’m pregnant.

I am 13 DPO now and period is to come today but used LH test to see what would happen and I know last time near my period time there was no second line but now I tested on the day my period is due and there is a second line.

I know if your hcg is positive it can show something on the LH test.

And yes I know the test is negative for sure but why is it showing a line either way?? Just curious lol