While it is important to have a well-rounded diet while pregnant, you shouldn't feel obligated to eat things solely because they're nutritious. If you're not hungry for it, then your body doesn't really want it, and a good prenatal vitamin should help cover for anything you don't get through your normal diet.
With my last pregnancy, I found that it was easiest to just go with my cravings, but try to find a healthy option for them. While I normally love salads and fresh fruit, I just wasn't hungry for them throughout the pregnancy. I suddenly craved meat, cheese, sweet stuff, peanut butter, and other high-calorie and/or high-protein food. For the meat, I just tried to edge more toward poultry and bison and away from higher-fat beef, pork, and processed meats. Blanched vegetables that had some of the meat flavor on them helped get those veggies in that I no longer craved. I tried to focus on honey, breakfast cereal, and juices for the sweet stuff so that I would be getting something beneficial in there too, and still ended up with a lot less sugar than allowing myself to gravitate toward candy or soda pop.
Overall, I ended up being much healthier with this pregnancy than I was with my son (where I did attempt to force-feed myself with the strictly nutritious), and felt a lot better. Whenever I ignored cravings before I tended to feel sick or lacked energy. Now that baby is born, despite breastfeeding, my tastes have immediately gravitated back to fresh fruits and veggies and away from the higher-calorie stuff -- again, the body knows what it needs :).