There are definitely lines on all your tests. When very very early, the difference in line darkness can be minimal if there at all.
This is because very sensitive tests show a line from 10miu, but the difference between 10miu and 20miu is virtually non existent, then there's the issue of fluid intake and urine dilution day-to-day.
It is, of course, possible that your pregnancy is unfortunately not progressing as it should be and will result in a chemical pregnancy, but that's not guaranteed just because lines aren't getting darker yet.
It might sound counterintuitive but try on higher sensitivity tests, you can also try a clearblue digital to get a definitive answer as to whether you are currently pregnant or not (I'd say you are).
My line progression was pretty much nothing over 3 or 4 days, but I'm very much still pregnant.
Oh, also, I believe frer has been discontinued in the UK. You can buy them on amazon but they could be fakes. Boots one is now actually considered the best early brand. I just used cheap £1 clear and simple midstream tests (but I dipped them).