Needing extra calories!

I'm 5'4.5 and 150 lbs.  My caloric intake should be around 1600 to 1800 because I'm quite active, but I just can't eat that much.  I eat breakfast, lunch, dinner and two snacks and adding them up barely ever reaches 1,000.  I'm afraid that I'm sabatoging my weight loss because I'm not getting enough calories to fuel my body, but I just can't eat 1800 calories a day!  Should I just start upping my portions?  What do you think I should do?  I've tried nothing and I'm all out of ideas. 

UPDATE: 

Breakfast:  1 egg and 1 slice of 12 grain toast.

Snack: banana, yogurt and a cup of blueberries.

Lunch: Chicken or Veggie Sandwich with no fat cottage cheese and a handful of grape tomatoes

Snack:  cup of skim milk and an apple with peanut butter

Dinner: Chicken, stir fry, rice or Chicken, salad and baked potato

       &nb sp;    Steak, salad, baked potato (nothing on it but green onion)

       &nb sp;    Whole grain spaghetti with homemade tomato sauce (lots of veggies and very lean ground beef)

That's pretty much a typical day of eating for me.  I don't get it, everything looks so plentiful lol.

If you post a sample menu of a typical day, you'll probably get all kinds of suggestions.  If you're eating anything labelled "low-fat" you could switch to the full-fat versions, nuts, oils like olive oil, any healthy fats (peanut butter), check out the calories on different fruits - some are much higher than others same with veg.

You can increase your protein intake.  Even if it is just a protein shake or adding protein powder to yogurt or the milk in cereal.  I think it is about 120 calories per scoop of protein powder that would help increase your calories and add about 30 grams (give or take) of protein to your diet. 

add little things to your diet, it might take a bit to adjust to the portions but give it a week and see how you feel.

i would: add an egg to breakfast and maybe a bit of jelly on your toast(or whatever you like, apple butter etc.)

if you're eating a sandwhich add a couple of slices of an avocado on it, or get a denser grained bread with a bit more calories per slice.

add a granola bar to your snacks, i like the 90 calorie quaker chewy bars, or have fiber one, they are 140 cals but as the name suggests have a lot of fiber. or a handful of almonds/pecans/cashews whatever you like. dried fruit is good also.

and maybe add a bit of dressing to your salad, basalmic vinegar and olive oil. if all else fails and you're still a bit short at the end of the day, have a half cup of fat free sorbet, haagen daz makes good ones (i like raspberry)

It might sound like im suggesting you add a lot of fat to your diet but i assure you, it is all good fat. avocados do great things for your skin and oilive oil is much healthier than canola oil etc.

good luck!

:) Ive always said to people I talk to....if you dont feel like your eating to much, you're not eating enough. :)

Anyways Suggestions:

Breakfast: instead of 1 slice of 12grain toast, try to up this to 2
and put 2 tbsp of peanut butter in between :) if you can't up it to 2, then
you can do 1 slice with 1 tbsp of peanut butter

2tbsp of PB =~ 188cals, 16g of fat(3.4sat, 4.5 polyunsat, 7.7 mono, 0 chol, 6g carb, 8g protein)
Polyunsat and Monounsat have very good healthy benefits, the 0 cholestorol is an added bonus

Lunch: Add 1 tbsp of olive oil to your sandwich. You'll barely taste it but you'll get the calories.
And you won't even feel like you're eating more.

1 TBSP Olive Oil =~ 119cals, 13.5g fat(1.9 sat, 1.4polyunsat, 9.8mono, 0 chol, 0sodium, 0carb, 0protein)
Olive Oil is AMAZING.

Dinner:
Salad dressing: 2parts olive oil, 1 part vinegar, pepper
Baked potato: A baked potato always tastes better with butter :P (use a low fat low cholestorol margarine, i looked at the label for one the other day, and it was suprising, its actually not that bad)

Daily:

Make a drink  1cup apple juice, strawberries, blueberries, flax seed oil(good fats), apples, peaches. I keep a container of this in my fridge.

Meal Replacement Powder - Used a lot in weight loss, its basically a meal in a cup. It shouldnt replace all your meals, but, you can add this in as a drink during the day. Basically you add the powder to water or milk (i use 1%) and its a cup of ~300cals and a TON of nutrients. Theyre really good.

Replace some of your water intake with a juice.

These little modifications are more than enough to help you hit your calorie goal.
You have to eat 1800, some days...I have to eat 2500. Imagine how that goes for me :)