Have small  4-6 meals a day.  Include nuts,  fruits,  vegetables especially  greens. If you are a  non vegetarian have boiled eggs and fishes. This should help and please check with your gynaec too.

If the baby is gaining weight then if mom is not then we don't worry. Also if you have started your pregnancy over weight then you may not gain or gain very little during pregnancy.

have u checked the same with your doctor.  please consult your doctor for the same dear.