I had that with my last pregnancy. I got a couple of positive home tests when I was 4 days late then negative blood tests a few days later. They said it was an early m/c, but it took my body a while to realise that I wasn't pregnant, so I went through a few months of early pg symptoms. They tested my hormones which had the full profile of someone who was pg, but no hcg - so all the homones that the mother produces, just lacked the baby to go with it. At least I had proof it wasn't all in my head

Seems the pg switch was turned on but not off again. It took a few months but gradually came right.
I would also another week then go to back and ask them to test again. If it's negative ask for a hormone profile test to be done.
