Most Helpful Guy
With this situation you have right now, there's nothing that HE can do to help you. Because no matter what you do, your emotional turmoil will dispel any positive effort he makes.
Self-esteem building imo is all about focusing on your positives (the easy part), and accepting the negatives and not-so-rosy parts of yourself (the hard part).
If your size bothers you, and you want to lose some weight, make gradual changes such as drinking less liquid cals and going for walks around the neighborhood. Even that simple change may boost your confidence initially! :)
Im not trying to harp on your size, I just noticed that as the main cause of your insecurity in this question.
Pretty much the solution for this is self-esteem building.
Think...what have you been good at? What do your friends and family members say good about you? What are your hobbies, abilities and topics are you are knowledgeable about?
Now think...what things do you NOT like about yourself? Are these things you feel are able to be gradually be eliminated from your sense of self? If not, are you willing to accept your imperfection and own it because that makes you an authentic person?
I hope my rant helped you out, QA. I don't like hearing about women having low self-esteem, so I do my best to help! :)