Bump measurements

Amy • George Westlake, born July 10. Weight: 6lbs 9ozs. He is perfect! Now for the next part of this amazing journey.. 🌻💙
Hello ladies! 
Just a quick question. I'm 27 weeks and I am yet to have my bump measured! I rang my doctors on Monday due to not being able to get hold of any of the 3 midwives I have seen! My doctor said I should have been measured from 16-20 weeks and then it every midwife appointment after that. I've had 3 midwife appointments and 1 doctor appointment and no one has measured me! :( ive been told that the measuring is done from just under your bra line all the way down to your pubic bone? And it should be in line with the amount of weeks you are.. Example; 27 weeks = 27 cm (or 2cms either side of the amount of weeks) is this correct? I've been told at both my scans our baby is growing above average but no one seems worried about this and no one has really told us what this means, do any of you ladies know & could you please explain in a bit more detail to me about what this means? I'm 27 weeks and my bump is measuring between 32-36 cm's each time I have measured. I'm worried as this is a lot more above the amount of weeks I am. Sorry to ramble on ladies, I'm a first time mum who has had 3 not very helpful midwives and I can not contact any of them easily :( advice would be amazing! Thank you so much xo