Empress, I'm in a sort of similar situation myself. Basically my relationship with DH is OK - I do love him and he's a good father, but I don't really fancy him any more. He's never been exactly slim, but has really piled on the weight since DS was born, and I've ended up feeling like, "Well if you can't be bothered to make a bit of an effort for me, then why should I put myself out to summon up some physical desire for you?" Not very nice I know, but I can't help how I feel. Since becoming a mum I've struggled to keep myself looking nice, partly for myself but mainly for him, and yet he seems happy to just slob around in clothes he knows I hate, eating and drinking whatever he wants whenever he wants, and thinks that if I don't fancy him quite as much as I used to then I must be really superficial.
Doesn't take a rocket scientist to work out that these sorts of feelings go hand in hand with other problems in a relationship, but actually I don't think it's realistic to say that if you love someone, you'll desire them whether they're 12 or 20 stone. I do still want sex with DH occasionally, but it's only when I'm feeling especially affectionate and never because I just look at him and think Mmmmm. Given that I've always been pretty keen on sex, I find this really hard. But then, we have 2 children together, we get on well enough, have a nice life together, and I can't bring myself to throw all that away just for the physical side of things.
Rambling a bit and don't really have the answers - I think the answer is No, you can't MAKE yourself want someone - but you can make the best of what you have. In our case, after a year or more of subtle himts, encouraging weight loss on a health basis and so on, I basically pointed out the fact that people do tend to look better if they're not carrying a couple of stone of extra weight, which of course didn't go down well and now we have all sorts of pointed comments about it. It's horrible, and I'm just trying to back down and focus on all the things I do like about DH, who is a lovely man at the end of the day. Just a self-indulgent one!
Has your relationship up to now been a very physical one? And who is the more sexual partner? Is your DH/DP feeling neglected? In my case, I think a large part of DH being overweight is that he's depressed - but he won't admit to it so I can't really get anywhere with that. If you thought you were going to feel like this for the rest of your life, could you live with that, or would you decide to end the relationship?
Sorry still rambling better finish. Thinking of you though