Confused

I had a confirmed pregnancy test around 3 weeks ago from my GP. They took my bloods and had a reading of well over 1000 hcg. I received an appointment through to see the midwife for my first prenatal care appointment. However yesterday evening I discovered some very light brown spotting. I panicked because of this and went to my out of hours to get checked out. When they did a urine test the pregnancy test they did was negative. I don’t know what the hell is going on- could this be the start of a miscarriage. Has anyone else experienced this?!