Spotting....

So I'm 5weeks 3 days, had a MC in August and so this time around my doctor has been checking my blood work every so many days... I just got my results from yesterday and everything looks good... But then today (Bc I'm paranoid and check every time I go) I had brown liquid on the toilet paper... It's very light almost ran colored and not like mucus or clots... Doctor says I'm set for an ultrasound next week but now I'm kinda freaking out... Ugh... I know it can be normal but whyyyyy