Gaining back weight, and I need to stop

I saved lots of money. I took 2 weeks off from work. I started out at 266 lbs. I got down to 143, and now I'm back up to 178.  
 
I feel like a horrible lazy person.  I am trying to take the steps to be better. I know that if I had exercised this whole time I probably wouldn't have gained back as much as I did. I prayed and prayed for a way for me to be an active human being. I have never liked to exercise, but I want and NEED to love to exercise in order to remain healthy.  I'm training for a half marathan for Lukemia/Lymphma foundation. but I need to do better. I have missed several training sessions. I need a kick in the pants adn wake up. I just dont know what's wrong with me.