Faint line

I'm on day 53 of my cycle, I have mild pregnancy symptoms, for 2 weeks I've taken a test every couple of days, all BFN, yesterday morning I took one and I though I saw a very faint line but like a minute later it was gone. That afternoon, after feeling very nauseous, I took another one and the same thing happened. So I bought a different test. This morning the same thing happened. Faint line and then it disappeared. What can it mean? This was with 2 different ept brands