Help please

So I had a positive very faint but positive. Went to the doctor and there isnt a baby yet so they said wait and come back because it was too early to see baby but to continue to test at home to get a line progression. I started bleeding yesterday and I’m scared I think I’m having a miscarriage my doctor said to keep doing a line progression it could be a number of things making me bleed not a miscarriage. Do you guys think this is likely and does it look darker from top to bottom