That definitely doesn't sound like enough calories. Either you're not eating enough, or you're not calculating portion sizes properly. The thing that always gets me is when I eat/drink a small container of something and then look at the nutrition label and see "150 calories" and think OK, that's 150. Oh, wait! it's 2.5 servings per container!

I use http://www.calorieking.com for calorie and exercise tracking. It's not free like fitday, but it's fairly economical (something like $30/year) and the improved database and user interface is worth it to me.