Not sure if this matches up with your dates (I think I got a bit confused about when you may have ovulated there?) but from what I understand when an egg first implants (about 7 days after you ovulate) you get a surge of pregnancy hormones, which die down a bit over the next few days, but then increase again about the time your period would be due - so when a pregnancy test will pick up the hormones.

When I got pregnant with my DD I had symptoms starting about the time of implantation - so in theory when I was about 3 weeks pregnant - that lasted about three days. This coincided with the early surge in hormones. Then my symptoms went away and didn't return about till after my period was due, so maybe when I was 5 weeks pregnant?

I don't think this pattern is necessarily obvious in every pregnancy because I have got pregnant twice since then and didn't notice any of the early surge symptoms, only the ones that appeared after my period was due. But just thought I'd let you know there is an explanation out there that may explain it, though as I said I'm not sure if your dates match up with that theory......

Good luck...x