I've been having a lot of anxiety over something similar. All I can tell you is that the early ultrasounds have been proven to be off by 5-7 days, max. Extremely accurate. If you have had multiple ultrasounds in the first trimester that all match the same conception date / due date then I would go by your ultrasounds. I wouldn't worry much in your case, not with multiple first-trimester ultrasounds. Don't read into too many things online, or you'll find a reason to overthink. I personally believe it isn't the first guy you mentioned.
Three ultrasounds is a lot of evidence. What is it that is bothering you about the situation?