Positive test then line disappears?

I took a first response today and it was positive. Very faint line but it was there, my husband saw it too. I didn’t have any more tests so I went to the store and got more. When I got back the line was gone on the test and the next two tests I took were negative. Has this happened to anyone?

Little background we are not currently TTC. I am on the pill and have been for 6 weeks and take it religiously. No reliable info on when my last period was because I have PCOS and endometriosis so my periods are totally random. And the pill I’m on is jolessa which stops my periods completely. Going to take another test tomorrow morning. Any thoughts?