Ultrasound 5 weeks??

Hi everyone I had a ultrasound on the 8th of august my dr thought I’d be around 7 wks pregnant from my last period being 18th -24th June but the ultrasound showed nothing but a sac and that measured at 5 weeks the lady that done my ultrasound said it could be a missed miscarriage and to book in with my dr to get more test done so I went to my drs yesterday and he seems to think it’s a missed miscarriage too… he doesn’t want me to have bloods or a ultrasound done until another 14 days but it’s killing me not knowing if I’m pregnant or have miscarriaged

I am still breast feeding my 16 month old mainly of a night to go to sleep could it be possible that because my body hasn’t gone back to normal from first pregnancy that I ovulated late? And I’m maybe 4 weeks pregnant so it’s to early to see on the ultrasound? Has this happened to anyone else before and everything been fine ??🙏🏼