26 weeks pregnant: why am i feeling like this sometimes?

it is the second time this happens in my pregnancy but all of a sudden i get like real nervous and i can feel my heart beating faster and i start to breath hard. what is so weird about it is that when i get like this i feel the need to eat sweets. the first time this happened i went straight for the lemon flavored potatoe chips and brownies and i was eating them like a fat *** until my husband stopped me. second time i was cookin in the kitchen and the first thing i thought of was making myself some chocolate milk. i drank the first cup in a flash (drank 3 total). i dont know what the hell is wrong with me and why this has happened all of a sudden when im just normal. its kinds like im having a nervouse breakdown but i dont know why i act like that towards food when it happens. its like something just hits my body all of a sudden