Have jean sizes changed again?

So, I've been wearing a size 12 jeans for a few years now. Two years ago I was 159, right now I'm 152. I've pretty much learned that I can't lose weight unless I'm at about 900 to 1000 calories a day and even with that it's only like a quarter pound a week :-( Anyway... so, I've been the same size jeans for a long time. I needed a new pair of jeans so I went to buy them. Size 12 doesn't fit me anymore?!?! I pretty much need a 16 now?!?! How is that even possible? Have sizes changed recently again? I weigh less than I did even though it's only a few pounds. I should still be the same size. I have another almost brand new size 12 that I bought a year ago that still fits fine, I've only worn it like twice because the dye keeps coming off on me. But it fits. It's not stretched out or anything. Same brand same style at the store does not fit me anymore. I had to go up two sizes????? Does that even make sense to anyone else? Got so depressed I refused to buy jeans so I went home drank two cans of pepsi and ate a donut. :-( I just don't understand. And now I feel I have to starve myself so I can fit into jeans that should still fit me. I'm not exercising, not getting muscles that would make them not fit. It's so depressing.