Weight gain/ diet

I'm planning on having a natural birth, I eat well 85% of the time, walk twice a day when I can and I nanny for two kids so I'm always on the go... I'm currently in my second trimester I've gained 4 pounds between each visit the last two visits I had. So 8 pounds in two months.Which I thought was normal, a pound a week. Prior to this I was low/average weight... I was told I need to stop having such leaps in weight gain and save it for my last trimester, if I can't stop the weight gain then my body might not be working properly..I don't understand this, I've gained weight just in my belly, my BLood pressure is normal and I have no swelling in my hands or feet. I do like to have ice cream once and while but is that really going to effect the birth I want to have? Sick of feeling guilty for my weight and what I eat... Anyone have a natural birth and not eat great all the time? Or anyone elses Dr giving them a hard time about weight?