Ultrasound dates off but sure of dates

Ive had 2 miscarriages in the past year so was nervous about my 7 week ultrasound today and was so hopeful for good news. They saw a baby measuring 6 weeks 1 day with a heart beat but they were unable to count beats per minute. I would not be so worried but I'm pretty certain of my dates I took ovulation tests, had implantation bleeding at 3 weeks 1 day and bfp at 3 weeks 2 days so it would be basically impossible for the US dates to be correct. Has anyone been here? Would love to hear stories both good and bad.