Could just be early. With my 3rd in 2019 I wasnt due on till 22nd October but I just felt pregnant really on and had tests so I tested really early too and got a faint positive (just like yours) on a FRER on 13th October, I done a CB Digi the next day but that was a negative and a couple of cheapies were negative too. I thought maybe I was just being insane but I just felt so obviously pregnant. I'd been sick a few times, had strong smell aversions etc. I waited a few more days and tested again and the line got darker. By the day AF was due I had strong lines on FRERs and the CB Digi confirmed positive too! So fingers crossed it's the same for you!