Weight

So i just wanted to get some feed back on this . Im 34 weeks tomorrow and since i been pregnant i havent gotten morning sickness or anything. I just been getting really bad heartburn latley that occasionally makes me puke. I have not gain any weight i either lose or stay the same . Is that safe or does that mean my baby will be small.? I dont really have a good appetite when i eat i eat verry small and get full soooo fast i never finish eating and i stay full for most of the day . Any one else going threw this? P.s this is my third baby and i never had this happen.