Confused about miscarriage and scan

So at 5 weeks I started heavily bleeding red and cramping, which was two days before my previously scheduled ob appt that should have been to confirm the 7 bfp's I had in week 4...I gave a urine sample which they never told me the results on and instead my doctor gave me a transvaginal ultrasound. I was spotting red that day (after two and a half heavy bleeding days) and he didn't find anything except a good looking thick uterus lining - no sac or anything like that. He took a blood sample and i'm waiting for the beta results. I assumed chem preg or very early miscarriage before i even got to the office, BUT now I'm confused while i wait because how could my lining be thick AND I had just bled as much as I did? He showed me the screen and explained everything we were looking at. I didn't think to ask him until I got home, but i was wondering if anyone experienced bleeding and had a healthy lining at the same time?