HELP

Eat what you can.

First of all, MFP expects you to include activity at work (such as walking all day) in your overall activity level (probably active, or at least lightly active), and then you don't add it a second time by logging it as "exercise." So if you said you were active or lightly active, MFP is probably already taking those steps at work into account (or party into account, if you told it you were lightly active).

If you're having trouble consuming enough calories, try eliminating any "diet" foods you might be eating and substituting "regular" food. Also, include more calorie-dense food in the form of healthy fats, which your body needs. For example, cook with a little olive oil instead of steaming things, have a handful of nuts or a spoonful of peanut butter as a snack, add some avocado to salads or sandwiches, and switch out some nonfat dairy products for reduced fat or full-fat versions.

I rarely eat many of my exercise calories. I do eat snacks as it seems easier than getting everything into 3 meals. At the end of the day, if I'm still low - i check my nutrient ratios & see if I can find a snack to boost anything that's low (trail mix for added protein or fiber, fruit for more carbs, ....).

Very likely you are not measuring your food correctly. Do you use a kitchen scale (accurate), or do you guesstimate quantities (not accurate)?

Could you try adding 1-2 small snacks throughout the day to get your calories up instead of trying to make one of your big meals even bigger?

+1 on the peanut butter and avocado. Another poster in another thread recommended eating chicken WITH skin and I thought that was an easy fix. I wouldn't have thought about a higher % milk but that is smart and easy too!

As for your sweet tooth-- I have that problem as well. I've found that the only way I can get myself to stop craving the candy/cookies/cake 24/7 is to eat a ton of fruit during the day. I keep dark chocolate squares in the house for emergencies.

I wish I had the problem of not being able to eat all of my calories! I can ALWAYS find ways to use them up.

Peanut butter, avocado, nuts and cheese are great ways to get several calories in a small serving plus they're all good for you. A medium banana is about 100 calories. You can use full fat dairy products to add more calories too. If you drink tea or coffee, sweeten with sugar or honey.

I'm not a nutritionist so what I say is just based on my experience.
When starting out, don't worry about eating too little. As long as you're not hungry and you're eating real food (not junk), don't force yourself to eat more. When you get closer to your goal, you might have to be more careful about this. But when getting started, the main objective is to learn which foods fill you up and which food just makes you crave more. If you get used to eating more snacks or bigger meals to consume all your calories, you might find yourself struggling once your allowed calories comes down.
When I started I was allowed 1960 a day. I was getting comments all the time that I'm not eating enough. At first I started eating more but realized I don't need it and my weight loss was stagnating. I went back to what I was doing and I've been losing fine since then. Over the first 3 months I averaged about 1200 calories a day (I'm 5' 11").
At this point just go with the flow as long as you're below your calories for the day.

Just my two cents.