Dark test lines

I just confirmed pregnancy at the doctors. I’m 3w6d but I won’t get an ultrasound until I’m 6w. I’m ok with that but I’ve had 2 miscarriages and a chemical pregnancy before getting pregnant with my 10 month old. I have taken tests but they are really dark. I never got tests to get that dark until I was close to 6w. The First response I took was 8 days before my missed period and the Walmart cheapie was taken a few days ago. Is this normal and I’m just over thinking? I ask because twins run in both sides of my family and triplets on my dad’s side. I’m more than a little nervous of multiple. I still haven’t missed my period yet. It was suppose to come on this coming Saturday.

Edit: They did a blood test yesterday 1/10/19 and told me my hcg levels were 228. I was 3w6d. My levels were never that high with my previous pregnancies until around 5 weeks. Hopefully these two weeks go by fast.