Need help with daily diet plan to lose weight !?

Im 19 years and unfortunately Im obese ! Unlike any other teenager I cant simply exercise as I have spine problem. So, I've been told by the doctor not to exercise. But what worries me is that Im gaining weight ! My thighs and ock seem to be growing bigger and my body looks out of proportion. And I really have no idea on what diet I should start with. For the past few days, I've been eating cereal for breakfast, chicken soup for lunch & tuna sandwich for dinner. But, I cant go on like that as I am now having gastric problem ! Could anyone out there please advise me on what to do. i need a daily diet plan starting from breakfast till dinner. I need to lose this weight as my spine problem is getting really bad.