First off I can see why you are a little concerned. If it was me I'd hope to see a bit more progression with 3 days between the tests and for the lines to be darker by almost 5 weeks. That is just what I would be hoping for though, it doesn't mean everything isn't fine.
In the second lot of pics the second one does,look quite a bit darker. Are you compairing different brand tests? Different brands can give a huge variety in lines so I wouldn't try and see anything from compairing them. Are they cheep internet tests? Some ICs are really bad for giving a dark line and stay faint for ages. Also you can't compair a wet test to a dry one and pics can vary because of the amount of light etc so it gets tricky. If it was me I'd go out and buy a FRER because they are good for giving a good dark line and everyone uses them so it gives you something to compair to. Otherwise wait another 2 or 3 days and test again with the same brand you are using. By then I would expect to notice the difference. Or try and get bloods from your doctor.