I’m so confused

I just had a baby 7 weeks ago… I started feeling weird and crampy but my period never came so I took the first test two days ago it came back positive. Then I took another test the following day and it was still positive but much more faint so I figured ok it’s a chemical, then I tested again this morning and the line is darker again so I have no clue has anyone had experience? I asked my dr if it could be leftover hcg from the pregnancy and he said no