I don't get the replies that staystrongskyscraper is getting. To me it didn't sound like she wanted nutrition advice, but rather trying to address the issue of her feelings and thoughts about food.
I don't have any experience with eating disorders (not that I'm saying that you have one) so I don't think I can help much. I would like to ask some questions though as I am kind of curious. If you are not prone to gaining weight, it will be difficult for you to do so, especially if your working out as well. Even if you wanted to be absolutely sure, figuring out how many calories a person of your size should it and then eating that amount every day will make it impossible for you to gain weight. I'm just curious, if you did that and saw that you didn't gain any weight at all (and still stayed at a comfortable and healthy weight), how will that affect your way of thinking? If you know for sure that you won't gain weight, will the irrational fear of gaining weight still be an issue?