Am I having a miscarriage?

So yesterday I went for an early scan as wanted reassurance everything was fine and she said baby was only measuring 5-6 weeks and couldn’t yet see a heartbeat. I thought I was 8 weeks. She said not to worry as dates can be out and go back next week as it’s too early to see heart beat. BUT I definitely ovulated 19th June and then took a how many weeks pregnant test on 11th July and it said 3 weeks (post conception). So I have to be more than 6 weeks. Is there any hope or has my little bean stopped growing?