6W6D no heartbeat

Very complicated story but to sum it up I have a 9 month old I’m currently EBF, last MC was 1/14/20. Periods are irregular or nonexistent when BF. So basically I got a positive PT, scheduled an U/S the next day. They’re strictly going off of my last period and saying i should be 21w3d but my sac is measuring 6d6w and they told me I’m miscarrying! Most places won’t even do an u/s until 8 weeks so I’m confused on why we are rushing a heart beat. They tried to schedule a D&C and I refused because I feel like I need to wait longer and get a second opinion! I’m having regular pregnancy symptoms, no pain, no spotting! They made me feel REALLY uncomfortable even gave me a little doll and told me “this is the size your baby SHOULD be”... I’ve been an emotional wreck all day. Although this baby wasn’t planned & is very close to my youngest I want to love and care for it like I’m supposed to! The thought of miscarrying again breaks my entire heart💔 just needed to vent 🥺😞