(Well, with my first and only biological child I gained 69lbs. I am 5'8, started at 130lbs and went to nearly 200lbs. It took a year and half to get back to a weight I was comfortable with, and two years before I was 135lbs (where I am now.))
Here's the thing. When you're pregnant, your body prioritizes the fetus over you. It is also is stocking up, in case of famine or illness; if you have extra weight, you can go longer before your milk or body 'dries up', should you not have access to proper nutrition for a while (so you will gain weight more easily when pregnant than not). But that means, if you don't get enough calories and nutrients, your body will rob itself to feed the baby. That will last a lifetime. Your bones and muscle mass will suffer damage. You will experience more of an inability to stay at a healthy weight (if your body is starved once, it will go into lock down mode over calories later to make sure it doesn't become starved again). Your future, as much, if not more than your baby, will be affected by not gaining enough weight.
Every woman, during every pregnancy, has her own healthy weight. More for some, less for others. Some are going to have more water weight, a bigger fetus, bigger placenta, more amniotic fluid, bigger breasts, etc. Others less. You and your (trusted) health provider need to talk over what that looks and feels like for you, during this pregnancy. It will likely be more than your last. (BTW historical interpretation of healthy weight gain changes - according to my SO's Granny, you weren't allowed in the military hospital if you gained more than thirty pounds total during pregnancy. It was considered high risk. I don't know for sure if that's true, but it's insane!)
I don't think you sound superficial. But, when you said, "I will gain 29 or 30 which just makes me sick," I thought, uh oh, that sounds worrisome. You're not alone in your concern and there are many women who share your concern. It is okay that you feel the way you do, but it isn't *necessarily* healthy, especially for you. So, I applaud your honesty and see it as being brave. I do think looking into this a bit more might be beneficial. Good luck and congrats on your new baby!