toning up is the hard part

I've shed 35lbs. in the last 5 months by counting calories and by substituting low cal foods for the not-so-healthy ones. Yes, I've been successful thus far, but I cannot seem to commit to a regular exercise plan for more than a week or two. It seems like no matter how much I excersize, or how many crunches I do, I cannot get rid of my droopy baby belly...it's embarrassing. I went from 210lbs five months ago to 175lbs today, and at 5' 9'' I appear tall and slender, but I have 0 muscle definition especially on my belly and inner thighs. I hope that long term commitment will be my solution. If anyone has any suggestions for me on motivation, toning, or exersizes to trim excess belly fat, I'm all ears : ) Try, try, try again....here I go.