frustrated

Figuring out how much you're eating now is key to starting to track what you need to do.

I use http://www.fitday.com to track my calories and it is VERY helpful to see what the basic percentages come in at (protein, carbs, fat) and how many calories I'm eating in a day.  Fitday will also give you a basal rate based on information you enter about your weight, age, lifestyle.  You need to eat at LEAST as many calories as the Basal Rate.  This is the amount of calories that you need to sustain your energy.

How much you need to eat depends a lot on body weight and what kind of workouts you do.  You may feel full but sometimes that isn't a good indicator, especially if your body has got used to a lower calorie diet.  I was eating quite a bit less than I am now (around 1500 calories a day) and was not seeing any results on the scale.  A couple of people told me I probably needed to eat more, I'm now at about 2300 average per day, and it's working a lot better.  I have more energy, I feel better and I'm actually losing weight.

General Recommendations for Endurance Athletes:

55-70% carbs (your main fuel source)
12-15% protein
20-30% fat

If you want to keep it easy, use fitday, eat at least your Basal Rate and fitday will show you where you fall on the basic percentages (I'm having success with a 20% protein, 20% fat, 60% carb goal.)

Try that for a month, if you're not seeing any progress, try something else.  Just from reading your post, I'd think you might be too low in fat (fat is very necessary) and possibly too low in protein.