They may do extra scans because:
you are overweight/underweight/petite
you have pre-existing health conditions
you have developed pregnancy related health conditions
your consultant likes to keep a closer eye on you
Try not to worry. I was overweight, have a heart murmur, was almost 41 and developed gestational diabetes. It meant I got seen every couple of weeks by someone and had scans every four weeks.
The pics of baby as you get further on are amazing. Focus on the positive. You'll have your rainbow here in no time.
Pip x