What Causes Nausea And Lower Back Pain Post Miscarriage?

Hi, I had a miscarriage about 5 to 6 weeks ago, and a D&C about two and half weeks ago. I had a negative pregnancy test three days ago, and my test this morning was a very faint positive. Is it possible I am already pregnant again? Or just leftover hormones? I feel pregnant . Compete with the low back ache, sick feeling, exhausted, my eyes have just been weird, and I m incredibly hungry. Thanks, hanna