Can you tell me how to tell my boyfriend i used to be fat?

Honestly: "Dear, here's a photo of how I used to look. I am so glad that I thinned down. I did it for myself, but I had no idea that I'd be so fortunate that I'd find love with a wonderful man like you." It's a fact of life -- men are most attracted to women who take good care of your bodies. I hope that as long as you are together, fitness will be a priority in your relationship.