Why am I so hungry all of a sudden?

So I have been on a modified diet (really just moving to a healthy diet with veggies and lean meat, and whole grain carbohydrates, and no caffeine) for about 3 weeks, I have been trying to eat 1800 at least calories a day, because at 195, 24 years old,  my BMR was about 1650 and I am also breastfeeding (an added 350-500 cal burn at sedentary).  It has been really hard for me to hit 1800 calories, but the last week I have been able to do it. 

The first week I lost 10 lb and attributed it to the massive change in diet, and lost water weight, the second week I started light cardio for 60 minutes a day 6 days, and didn't loose a pound,  this week I cut back to 30 min of cardio and a cardio yoga video for a total of 75-90 min a day every day but today.  I have been really tired, and after looking at what my BMR should be with the exercise yesterday, i figured my calories have been way low for my activity (I also have a 2 year old, so i'm always on the go!)  I've always been more of an exercise person than a diet person and have always been successful, but because I have had fatigue problems, i figured a better diet could benifit me for more than wieght loss. I usually try not to diet because of a past ED.

The problem is that this morning I woke up to get the baby, and stayed up instead of going back to sleep after i put him down, within 5 min of being up I was ravenously hungry, so much so that I had to hurry up with my breakfast and eat a banana early so that I wouldn't pass out.  (breakfast is always 2 egg whites with 1 tbsp low fat shredded cheese and 1 tbsp green pepper, 2 whole grain low fat waffles with sliced strawberries,  2 slices of canadian bacon, and 4 oz of v8 fusion light juice.) In addition I had a cup of coffee ( i usually have decaf tea)which i haven't had since Christmas.  At about 11am, i suddenly got so hungry, I was shaking, and again ate another banana to get the boost so i had time to make some more substantial food. (ham sandwich,with tomatoes and mustard on whole wheat bread w/ an apple and 100 cal pack of baked chips) The same thing happened at 1:30pm  I had a granola bar, and a hot pocket (lean of course) sandwich just to keep from getting really bad.

I still don't feel normal, does any one know why this is happening? does it have to do with the coffee, or am i just not getting enough calories? Or am I just eating the wrong kind of calories for what I'm doing? I would appreciate any insight to this problem.

Oh, and the fact that the episodes are so sudden is not a mystery, because of the ED in the past, and i literally don't usually feel hungry until I'm about to pass out, I normally set an alarm to remind me to eat, but these are unusually close toghther.

ok, first off let's clarify...you;re BMR,  is your basal metabolic rate, the number of calories your body would burn if you stayed in bed all day, so the exercise is not part of your BMR.  it is part of your total calories burned for the day. 

if you suddenly upped your activity level to six days of exercise a week, you are increasing your calories burned and metabolism and need to  eat accordingly.  If you are getting so ravenously hungry, take a careful look at how many calories you are eating and burning.  If you think you are eating enough and still experience this, I would see your doctor, especially if you are shaking and getting lightheaded.  If you are truly eating enough this should happen, and you need to have your doctor test you for diabetes or thyroid issues or whatever else he thinks may be the cause. 

I know, about the BMR, I wasn't really doing much before i started dieting, and my sedentary was like1900, but before I started watching what i ate I was barely getting 1500 calories, which is why I was surprised to have gained so much weight (outside of the pregnancy wieght) I just figured that I wasn't eating enough, and it was truly unhealthy food, so I started eating healthier, but the side effect is that I have to eat even more, which is really hard for me and I 'm still barley making 1800 cal (thats with a desert).  I knew I needed more calories, I just figured, I'd have to work my way up to eating more calories (not usually what you hear from someone on a diet). 

Needless to say this is why I avoid diets now.  I have never been good at finding the medium between healthy and healthy with enough calories.

Any tips on how to make my meals last a little longer, I can't be eating ever couple of hours, I'd never get a thing done!

Like fyrefairie said, first of all you need to figure out if you aren`t undereating, in which case you should definitely try adding some high-cal foods like 1tsp olive oil in sandwiches, nuts and dried foods as dessert/snacks.

If you are consuming a correct number of calories, try incorporating veggies as snacks - they are crunchy, filling, nutritious and low cal. If their natural goodness is not enough, some low fat dip would be great. I for one absolutely love carrot sticks dipped in mustard, or lettuce leaves lightly spread with tomato sauce and basil.

Also another thing to watch is your carbs/protein/fats ration. I usually find that when I am not getting enough fats or protein in my diet I am constantly hungry, no matter how many carbs I gulp down. Incidentally these deficiencies usually appear under a disguise of sugar cravings, so you just enter a vicious cycle of carb eating which never really touches the real issue.

yes, you definately need to make sure you are getting enough protein, carbs burn quick and leave you hungry, and without protein you will lose muscle mass.  as for healthy snakcs, i agree with ily about teh veggies with some dip, i personally like a good hummus with some baby carrots, trader joe's has some good ones!!

and i understand some days it is hard to get enough calories when you eat alot of lo cal healthy foods, it can seem like you ar econstantly eating.  use olive oil instead of butter (helathier fats and higher calories to get your number up there), or try pb or almond butter on your toast instead of butter or jam or dry, again its calorie dense but has the healthy fats necessary for your body. 

if you have a history of ED and a new baby, i would consult a doctor or nutritionist to make sure you ar eeating properly for your body and your baby;s (assuming you're breast feeding here).  Also, make sure you take a multi-v.  good luck

You could try taking a suppliment, I find they help me when my appetite goes crazy.  I have a link on my profile to the one I take.  Good luck girly!