Hungry but nothing sounds good...

So a little back ground: when I was pregnant with my son who is 5 now, I would go through periods of being hungry but not wanting anything to eat, or just not being hungry at all. This would last about 2 weeks and if always try to stay hydrated but on the opposite 2 weeks, I would eat everything in site! As a result the first part two trimesters of my pregnancy I didn't gain any weight and actually lost some. My dr was concerned actually and made me take measures to gain weight and I blew up like a balloon and was miserable!!