No need to worry. I also only gain 1 pound in the past 3 weeks. I am 32 wk and 3 days now. As long as Ah B is healthy and gaining weight gradually. It is ok.
You should check the weight using the same 磅 and at roughly the same time, ie. if you used to check before meal in the morning, then always do so.. If you change to night time and after meal, then obviously it will 重 多 d. Don't worry, just watch out your diet.
I went to doctor today and found some protein in my urine. Dr. said my blood pressure is ok so he is not too concerned.