Weird appetite

Hey guys so for the past month or so my appetite has been different than it usually is. I used to have a normal appetite I would eat regular sized meals not too big not to small. Now I eat the smallest portions, I literally take two bites of something and I'm full it's so bad to the point where my family calls me tweety bird because I eat like a bird but, I then get hungry two hours later.What's also weird is at night around the same time between 10-11 I get really hungry and I also get bad heart burn, it happens every night and idk why! I've also noticed that I'm losing weight, I'm not doing anything differently and I'm not trying to. I'm 5'2 and went from being like 135-137 to being like 120-123 in like 2 months, even my mom keeps telling me to stop losing weight because I'm going to be too thin. Can some one please help me! Sorry for the long post I'm just really confused:/