I know I had insanely high levels with each of my four kidlets, so much so that I had positive hpts well before its considered possible. With my last I had a digital hpt showing 4 weeks pregnant when that wasnt physically possible due to Dp being away until four days earlier, when I also ovulated. My GP felt the test must have been faulty, but a blood test confirmed I was pregnant.
I had extreme morning sickness to the point that I had maxalon injections twice daily until an emergency c-section at 37 weeks. I had numerous scans early pregnancy as the gp was positive it was twins, but there was definitely only ever one baby. All my scans showed him to be big and always two weeks ahead of dates so it was a bit of a joke with dp about what I'd been up to while he was away lol, as there was only that one possible night when he came home so the date was never able to be different unless I'd been up to no good! Thankfully dp trusts me, otherwise it could have been awkward! Luckily Ds also looks exactly like dp
All my pregnancies have been similar, and all have been healthy singletons so I guess its just the way my body works. Like a pp said, as long as the levels rise its all good