1st ultrasound and no sign of baby

Hello, i went for my first ultrasound today and the baby wasnt visible. The dr says im about 7.5 weeks but i am pretty sure im only about 6.5 weeks. The doctor made it sound like i definitely miscarried but my body hasnt caught on yet. The ultasound tech said not to come back for at least a week but due to the holiday they scheduled me for another ultrasound in only 6 days. At first i was devastated after this news but ive done some research and this might be common. Just wondering if anyone has experienced this or if anyone has feedback?