32 weeks tomorrow and gained 4 pounds

I went to the doctor Monday and she said I need to gain more weight. I lost 8 pounds or so during the first trimister. I was 140 pounds and went down to 131 or 132 the first trimister. Since then I've gained I'm at 143. Should I be concerned that my baby isn't healthy? From all my scans everything seems to be going great! This is the first time anyone has mentioned my weight. Mind you I went to this doctor 2 weeks ago and mentioned my weight and she Saud everything was fine now she's telling me to gain weight.