Hi, ms.cate... welcome!
I know that mentality all too well. "Everytime I start an exercise program, I get a cold, and then I have to quit. What's the point?" or, "I eat well all day, and then I screw it up with one binge... what's the point?"
I think you have to remember that we don't have any control over the future. None. But what you do today will affect who you are NOW. Right this minute, and that's what's important.
So
do what makes you feel good now. Give your body what makes it feel good. Good healthy food and some exercise. It's not the easy thing to do, but it's the right thing to do. Hang in there ... you can do this...