It's annoying isn't it. I had someone say the other day, 'oh, so you're around 5.5 months now aren't you?'. I'm only just on 4 months. But I really don't think they know what to say. I've even had someone comment that now my belly looks pg, as opposed to just looking fat!!
Try not to let it get you down. Your baby has the majority of growing yet to come, and baby (and you) will get a lot bigger yet, but it's the most important stage of your pg now, so try and cheer up a little and remember you're baking a beautiful little bubba in there, regardless of the size.

BTW ezz, happy due date!! Any niggles yet??