Please help me out :(

Okay ladies I just wanna know if this has happened to anyone before? I’m supposed to be just shy of 8 weeks pregnant, and went for my ultrasound this morning. The baby is measuring at 5 weeks 5 days. So I asked the ultrasound lady when that means I ovulated and she said about March 27th. I got my positive pregnancy test on March 26th! There’s no way. So my theory is that the baby stopped growing at 5 weeks and 5 days. Anyone have this happen and carry the baby to full term alive? Or has anyone had a miscarriage and didn’t bleed or cramp? I haven’t bled nor cramped and I did see the little yolk sac and that on the ultrasound. Anyone have a clue what’s going on? I’m so stressed out. My new due date is the 19th of December