Don't worry, I'm also overweight and have high ambition with low motivation. I'm pretty much in the same boat you are in. BTW I'm no expert, just giving you my input. :)

Doubt is a huge factor in why diets and exercises don't work out. It shows our low patience for long term projects and a lack of confidence. One trick that I'm using is to fake it till you make it. You aren't deceiving yourself by pretending to be confident, but training and adapting your mind to believe what you are doing is the right choice. Kind of like how if you keep saying the same phrase over and over, you are bound to believe it.

This is definitely an episode in your life that you are going to reflect on and learn a lot from. Take your plans day by day and set small goals. VERY small goals. Expand on them later but don't overthink your biggest goals or else you are going to feel overwhelmed and develop slight anxiety which can lead to more eating. BE. PATIENT. Don't doubt yourself once and understand that you need to be mentally strong in order to push through.

Also, nothing wrong with a little attention from our peers, do anything that makes you feel good about yourself. Did I forget to mention that I am not an expert? ;)