The measurements they do of your belly are not exact, they were more commonly used before they had U/S and what not, but Dr. will still measure. I have been measuring ahead also and Dr. is saying baby is a little ahead on weight but nothing to worry about. I also feel stretched to the max, but really nothing you can do about it! Just try to relax over the next couple of weeks and know your day is almost here!!
I would say 6lb10oz would be about normal. I had an ultrasound Monday at my appointment and I was 35w1d but baby measured 37w2d and was estimated at weighing 7lb2oz. My dr is delivering her at 37 weeks due to some issues. Personally I dont put too much faith into ultrasound measurements. At 36 weeks with my son they said he was already measuring over 8lbs and when he was born at 39 weeks (they induced me because they thought he was going to be huge) he was 7lb6oz.
I think it's pretty rare for people to measure at the exact number that they say you should be at. unless the dr is concerned about the size I wouldn't wory about it to much.
My measurements and ultrasounds are all out of whack with each other too. My belly measurement equals the dates guessed from my lmp, but from the ultrasounds I lose a week from that date...my other kids were 'late' and fairly big at 8lb3oz and 7lb14oz so I probably will deliver another bigger baby a week after the due date! (I hope not, I think after being late twice and having larger babies I deserve a wee 7lb er at 39wks or so lol)