I know for a long time I was very depressed about my weight, but for some reason didn't feel motivated enough to do anything about it. Ya know....I'd get on the scale three times a day and get off knowing I was gaining weight. My mom gave me the idea of keeping some bible verses in my heart and in my head (although the ones she gave me didn't help). If you aren't Christian I won't be offended if you disregard this part. Two of the things I wrote on my hand every day was that I was God's temple and God's creation. If I'm God's temple it means I need to keep the "temple" healthy. And if I'm His creation, it means I'm perfect in his eyes and I shouldn't be looking down on myself for being a little overweight. With this new found confidence I gained the willpower to become healthier.
Second, I started boxing classes, which let me have some distraction from any depression and I started losing a little weight and getting stronger. (It's also good for defense, so it benefits more than just weight) It's also very exciting and fun to me. So I'd recommend finding something like that (boxing, swimming, etc.) to look forward to exercising.