Tell me what you think?

Ok, so I had my 20 week Ultrasound last week. I talked with the Doctor today and found out that because of the measurements of the baby they have moved my due date back 3 weeks. So instead of April 18th it is now May 5th. I not very excited about this. Am I just being silly? I will go back to the Doctor in about 2 weeks and then in about 4 weeks have another 21-23 week Ultrasound. I don't know why this is such a big deal to me, but I am really bummed out. Please give me some input!! Thanks all!