I lost weight in 1st tri. I had only put on about 8lbs total at like 24 weeks. After that I put on a bit more, but I only gained a grand total of maybe 30lbs. 3 days after I delivered I had to go see my OB and got on the scale and had already lost 20lbs. Don't worry so much about your weight gain. It's not really indicative of whether or not the baby is healthy.
I also would not worry about your weight gain. I only gained a total of 5 pounds through the whole pregnancy. Peyton was over 8 pounds when she was born so I already lost what I had gained the second I delivered. Now I'm about 15 pounds under my prepregnancy weight without even trying... but everyone is different and every pregnancy is different so that may not happen to me again.
Re: weight gain 1st & 2nd trimester
BFP#2: 8/14/11 M/C 8/30/11 6w1d
BFP #3: 10/26/11
Beta #1 @11dpo: 22 Beta #2 @13dpo: 90 Beta #3 @17dpo: 480
Missed m/c 12w3d 12/28/11, d&c 12/30/11
dx Homozygous C677T MTHFR