Uterus measuring small at 8 weeks pelvic exam

I just had my first midwife appt at 8w4d. During the internal exam, she felt around for my uterus (can't remember what it's called, but had one hand inside and one hand pressing on my abdomen). She said my uterus wasn't measuring 8 weeks, more like 6, and that it can either mean my dates are wrong or there's something wrong with the baby. I was tracking ovulation and got my bfp before my missed period so am pretty sure of my dates. My first ultrasound is in 6 days (6/5) and I'm very anxious and scared. Has anyone experienced anything similar with a physical exam? Posting anonymously because most people don't know I'm pregnant yet. Thanks in advance!