Possibility that the OB is wrong?

Hi all, I’m estimated to be due the first week of April; however I think it’s more like late March. My last period was June 10, and my cycle had pretty much returned to normal by then. I also had the biggest, fastest positive I’ve ever seen-and it showed on the test damn near instantly. Though the ultrasound tech said when I came in that it looked like I was 6 weeks “on the dot” and decided to remove the date of my last period from the document/ultrasound thing. This is at least 3 weeks off from my math. I am 10 months postpartum so they chalked it up to my cycle not being regular and went with 6 weeks at the time. We are now at what should only be 11/12 weeks according to an April due date and for one; I’m literally huge despite barely gaining any weight, and I literally caught movement on camera that I sent to one of my friends for confirmation. Now, to clarify. This isn’t a full on kick that you would see like in the 3rd (or maybe late 2nd) trimester-this was like slow contractions, or like when the baby rolls over. I had to hold my breath to catch it on camera to make sure it wasn’t just me breathing. I had also been feeling movement inside to the extent that it brought my nausea back.