Hcg test confusion

I had a miscarriage on the 11th of July and after I had finished bleeding a few days later I started testing to make sure my hcg was dropping which it has been I had been still be getting positives up until the 7th of August when I got a vvvvvvfl which was near enough negative but then as the days of gone on it looks like the last two days have started getting darker.

Has this ever happened to anyone else or am I just being silly, I have been ttc since I stopped bedding but I wasn't sure that you could even ovulate with hcg in your system still?

The tests are from the top, the 7th, 8th, 9th and then today x