Motivation Needed!

I'm almost 21 years old my goal is to feel good about myself and to bring down my BMI, for my height I should be at 120 but I'd rather have muscle tone and be strong I'd be happy with myself if I got down to 140-150 by the end of the year.

I started off at almost 250 and I'm down to 217 now. My lowest has been 214 and now i seemed to gain three pounds back and I just feel sluggish. I know I need to exercise but I seem to have run my motivation tank to 'E' willing to hear any advice/success stories etc.