why isn't this working for me?

Hi there.  I am new to this site, but I have been counting calories on my own for awhile.  Even though I do this, I am seeing NO results!  Example, I have consumed 1398 calories today but went to the gym, as I usually do, and burned around 600 calories.  This is my basic routine.  I haven't lost any weight in over 3 weeks.  I just don't understand what I am doing wrong, but it's obviously something.  Can anyone help?

you are giving your body a net intake of only 800 calories when 1200 are required for the basic metabolic functions, therefore you are starving yourself and your body is probably holding on to its energy stores [fat] because it's in self preservation mode. you should be eating more or exercising less...optimally the eating more route is the choice to be made. what are your stats?

I feel foolish, but what do you mean "stats"?  Thanks for the input!

I believe by stats she means height, weight, age, activity level.   Those sorts of things.

With that information,  you can calculate your BMR (basal metabolic rate) to find out how many calories your body needs just for day to day normal body functions.

If you aren't taking in enough calories, your body will slow down it's metabolism to hang on to the calories that you do take in for energy since it isn't getting enough.  It sounds crazy,  but in order to lose more weight,  sometimes you have to eat more to get your metabolism fired up so that your body won't hang on to those calories. 

Thanks for that.  i am 5 ft 8.5 in, Weigh 151, 30 yrs old, and exercise a lot.  Run 35 min a day at about 5.5 mph and lift light weights for about 35-35 min.

When I calculate my BMR, does that give me the calories I need before exercise, or is it the total calories after exercise? 

I woke up and weighed in this morning and am actually up a pound.  I am on the verge of super frustrated.

I'm pretty new to this site too,  but based on your stats you sound like you are already at a healthy weight.  You sound like you are doing everything right though.  Consistancy will pay off.