Weight gain @31 weeks?

ok..so ill be 31 weeks on friday june 17th...i just had an appointment last week and i have not gained any weight at all.....with my son i lost 25lbs then gained it all back and gained 10 lbs he was born on his due date at 7lbs 14 oz....this baby is measuring at 35 weeks despite me only being 30 weeks and we know my due date is very accurate since my first us still had the egg sac they said its possible for it to be a day or so off but not 5 weeks lol....anyhow what did you all gain...anyone had a baby measuring 5 weeks ahead???