Hunger pains late at night?

So I can eat three meals a day, with maybe one snack if im hungry, but later on when its time for bed my stomach acts like I havent eatin all day! Im starting to think its the prenatal vitamins, I was taking them when I would wake up and id feel like I was starving all day with a stomach ache even after id eat, so I decided to take them before bed, and now im starving at night and it makes me feel so sick I HAVE to eat a small fiber bar. Am I the only one going threw this?! Im 7 weeks 2 days today.