I'm 27 weeks 4 days and I've gained about 25lbs already. My doctors are not concerned at all. Everything is going great and this is my first. I think everyone is different and we all don't fit the norm.
I'm 24 weeks and have gain 13 pounds, my doctor is not concerned. I think you are normal. Don't worry.
The ideal amount is 25-35. By the last 2 months or so you'll be gaining a pound per week. Just be careful I don't think its too much personally. If your pre pregnancy weight is normal you'll gain more weight than an over weight person who will gain very little to nothing.