Experiencing a plateau is normal during weight-loss. When I have them, I sit down and re-evaluate what I'm doing. Sometimes, I have to increase my calorie intake because of how much exercise I'm doing. During my TOM, I always know that I'm going to plateau the week before it starts (which annoys me so bad). The longest plateau I had lasted a month (I'm not trying to scare you), but it was because I wasn't really listening to my body. The key is to look at what you're doing, listen to what your body is trying to tell you, and see what needs to be changed.