About week 37 - it's when I noticed I wanted dinner followed by a cake 5 times a day also!! I just couldn't get enough sleep or carbs - I put on about a stone in 4 weeks, couldn't really sleep though as bladder was tiny. Was mind numbingly exhausted.
At 29 weeks, you might be low in iron. I recommend you take spatone in orange juice daily.
The first trimester was trying in a different way - I think it's because you're growing the placenta and baby.