Let's go for a run! ...

When I was younger like I just wouldn't gain weight and this also means just last year haha. But now I have realised that its starting to get to me. My ass has gotten bigger and my thighs tremendously. And well I am still skinny. But I want my old body back! Is it only me who just doesn't find the slightest motivation to work out even though you want to and you know that you need to...? I feel so lazy ! If any one has any good motivating tips let me know. I try to convinve myself at times.. when you get home go for a run, but instead I end up eating a whole bag of chips and lying in bed watchin a movie.... HELP.