Dark lines/high HCG

Hey all, super excited first time mum here. Getting a bit nervous though at how dark my lines have been so early and how high my HCG is. I know urine tests aren't 100% accurate, but HCG was measuring over 10,000 according to these at 4 wks, 5 days. I'm getting nervous it could be twins. My mum had twins so I have a higher chance than average. Anyone else had high HCG results like this but not having twins?