Baby TOO big?

trojas

So last week at my 18 week ultrasound (in which I received confirmation that it was a boy- woohoo!!) the tech told me that the baby was a little bit bigger than what they would expect for the # of weeks I was. I know exactly when my LMP was, so that's not the issue. But now I'm worried. I know it sounds stupid, but what if I'm diabetic? Or what if I can't deliver him naturally? 

People see me and can't believe how big I am and I'm not even 5 months. I know that every pregnancy is different, but I, too, didn't expect to be this big at this time.

Should I worry?