6w bleeding

Need advice. I am 6w2d through IVF. I woke up this morning with my underwear covered in brown/rusty red blood, that seeped through my pj shorts. I was immediately so upset. I called my fertility clinic and my first ultrasound isn’t scheduled until this coming Thursday and they said just to keep with my medication. It seems so far away. I have only had minimal brown spotting during the day. What should I do? Is this normal? I am so upset and wondering if this is the start of a miscarriage.