Pregancy

So I found my first ultra sound I took dec 28 I was 5 weeks 6 days but my last period was around nov 17 or 19 is that right because u no doctors be acing slow then around March was my last one I was 18 weeeks and 6 days now 30 weeks 6 days we'll really 31 and my d and c was in October I believe or September there saying August 24 I’m 31 weeks it just don’t make since but I think dec21 I was like 4 weeks idk just feel like I’m due before but does this make sense