Em,
Okay, I know everyone else has said it, but I had to add my 2 cents.
You are obviously funny, sweet, thoughtful, fun-loving, a great writer, and from your photo, a very pretty girl. Steve's porn problem is just that....HIS problem, and it has nothing to do with you or how you look. He was obviously using you as a scapegoat to deflect his guilt. PLEASE know that a man's attraction to porn is never going to be due to his supposed lack of attraction to his mate. It is HIS problem!! I'm not a psychologist, but I can make a good educated guess that his addiction to porn relates a heck of a lot more to his own self-image than to his image of you!
If you decide you would like to lose weight for your health, or to improve how you feel about yourself, by all means do it! Don't do it, though, for anyone else. It will work much better, too, if you are doing for yourself!!
In a healthy relationship, loving and respecting your partner come naturally. Appearances don't matter. I shared your story with my husband and he was horrified. I myself have put on about 45 lbs. since my marriage 19 years ago, and my husband loves me more than ever. I do want to lose weight (because I am vain, and I feel better when I'm thin), but I know that my DH will never change his feelings for me based on how I look.
You sound like you've got a very good head on your shoulders, and it sounds like you're moving toward making some good first steps to independence and self-esteem. All I can say is....You Go Girl!!
Hope you keep us all posted. We're here for you!
