What to expect at a 6 week ultrasound?

Saturday we got a BFP (YAY!!) after a miscarriage in November. So my doctor has scheduled my first appt and ultrasound at 6 weeks intstead of her standard which is 8 weeks. I was just wondering what to expect? I understand the baby won't be very big at all but can they see the heartbeat? Will they be able to determine if everything is progressing well? I'm trying to remain calm and positive but my nerves are getting the best of me