Boyfriend wanting me to go on a diet

I know I need to lose weight. My doctor makes that plenty clear. I've always been a bit bigger and never was the type to eat very healthy... But things took a turn a few years back when my dad died... I just started binging on everything. Binging is how I feel better. Me and my dad used to eat sweets all the time and sweets remind me of him. My weight and health took a turn for the worst these last few years and I can't see my feet which is humiliating to admit.... My last doctor visit he was a little harsh. My fasting blood sugar levels were 120 which is considered prediabetic. My doctor said if I don't start taking my health seriously I'm gonna have diabetes before I turn 30. I also found out obesity can effect fertility and wonder if that contributes to my PCOS.... My boyfriend wasn't mean when he said this at all but he sat next to me and said he loves me and wants me to live a long time and spend the rest of his life with me and that we should both start thinking about our health. IDK why he said "our" he's skinny as hell. He's not anywhere close to my weight... He is healthy... But he said maybe we could get on a diet together and it will be fun and that he's been looking into to the keto diet. I just smiled and held back tears. I know he's not trying to hurt me. I just want to break down is cry because I'm disgusting. I'm 5'7 and 583 pounds...