Hi, don't know where to start. But i had a miscarriage 4 weeks ago .?

The hospital told me to take a test a week later, so i did and it came back negative. Then the other day i was knocked of my bike, and while i was in the hospital they said my test was positive for being pregnant. I have taken another two tests and they came up positive faintly. I have cramps like period pains and have just sarted before to have a very dark discharge and my nipples realllly hurt. Do you think i could be pregnant again? Would love to know if anybody could help. Thanks.