I'll be honest, even 4-5 pounds can make a huge difference in how I feel - not only about how I look, but how I feel physically. Just those couple pounds can make me feel sluggish or my clothes feel...weird. I'm currently at the same weight I was in HS, or I should say, my lowest weight in HS. However, a few months back, I dropped about 8-10# lower (stress after the death of a family member, plus a very active job) and after spending some time at that weight, returning to what had been normal to me now feels, as you said, gross. As strange as it might sound, I've found that drinking more water than normal can help ease that feeling a bit... even if it doesn't change the numbers, it makes me feel healthier, and with that goes some of the sluggishness.