It's very easy to comment about this from the outside, if I hadn't had the experience with DD the first time I would probably tell you to eat healthy, workout and brush off their comments- but I gained 65 lbs with DD. When I went in for my 24 week appointment I had gained 27 lbs and my OB told me that if I didn't gain another pound I would be fine (unrealistic for the remainder of the pregnancy, but she was trying to get her point across). At 32 weeks I had gained 45 lbs and she threatened to put me on bed rest because I was 'swollen' (or just carrying a lot of extra weight...) I sat in the car and balled my eyes out, called my DH and he couldn't understand a word I was saying. Truth be told, I over indulged A LOT and didn't get the exercise I needed. Doctors probably just make assumptions based on weight gain, and it shouldn't be that way.
I have always had issues with my weight and body image- this time I worked out six days a week and hadn't had a carb in months before I got pregnant with DS this time. I followed a strict diet/workout regimen to maintain what i had worked so hard to get to. My body had adjusted to that lifestyle and the second I start adding in the additional calories, necessary (complex) carbs (i.e. sweet potatoes, whole grains) dairy, and cut the heavy weight training and sprints I started gaining a little weight. I've put on 14 lbs total, 2lbs from weeks 8-12, 0lbs from 12-16, 10lbs from 16-20 and 2 lbs from 20-23.
I'm sorry that they didn't offer more than just work out and watch your carbs, it can be hurtful. Let them know next time that you are extremely sensitive about your weight and that you are eating healthy and working out, maybe even complete a food diary for a week to bring to them in case they call you out again. I'd love to only gain 25lbs this time, but hell, I'll be happy with under 40 because I know how my body gains weight (I used to weigh 205 when I was younger, lost 70 lbs, got back up to 200 when I was pregnant with DD and lost it all again). If you've weighed more in the past your body has amazing memory and feels comfortable going back there, and it's harder to fight that as well. But you also know that you can always get back to that point as long as LO is healthy throughout the pregnancy, which is what your OB is there to monitor.
With all of the weight I gained, DD was born one day early- my OB was concerned she was going to be way too big with my weight gain so she induced and DD was born weighing 7lbs 10 oz and 22" long.