Well first let me say im no expert here ...but i see a few things.
1. you're doing wieght training so you're likely adding muscle while burning fat..muscle weighs more than fat so i would suggest you ignore the scale for a bit.
2. you might try doing weigth training only 2 or 3 days a week to stay toned and add a bit to the cardio..
3.you may not be eating enough ..i know its crazy but you body will adapt and store up for later demands if there isn't enough fuel for when you work out ..try a small prework out snack( banana or 1/2 peanut butter sandwich etc) and most important a post work out meal or drink ..be sure it has some carbs and protien to build the glycogen stores in your muscles back up ..
i had similar issues or questions when i started to work out again and these tips (from a trainer) helped me..hope this helps you ..keep after it:)
I have to congratulate you for the motivation and the strength that you have to do this for a month. Continue some form of regular exercise all throughout your life for proper physical fitness. Try to keep up the good work and remember all the good things you have learned and experienced till now and follow that earnestly for controlling body weight.
The calories you are taking are not enough to run a normal metabolism for long term.
You can take 1500 calories at least while continuing your strict exercise regime.
Your weight might be due to muscle build up and that is good as your fat is converting to muscle.
Check the fat content in your body with the help of your physical trainer.
Prepare a neat diet chart with the help of a dietician to give you proper energy, vitamins and minerals. Drink fresh juice and eat fresh fruit with fiber before and after exercises.
Keep track of weight and you will lose over a period of time. If you are in normal BMI and perfect physical fitness then it is very good!
I echo the others with both the kudos for being physically fit, but also echo them with the advice that you are clearly, clearly not eating enough to sustain your body for long.
Your BMI is 23.4, which is in the normal range.
You may also be overkilling yourself with all your activities. For what you want to accomplish, 3-4 times a week in the gym, 30-40 min of weight training and 20-30 min of cardio (switching it up as you are doing) should be fine. You may also want to add in some pool time once a week if that's an activity you enjoy.
Never go below 1200 cals a day. It is unhealthy to go below this level for long, and damaging to your body.
Give it a try for 2 weeks. You might be very surprised. Keep focusing on your lean meats, complex carbs, veggies, and fat free dairy, but be SURE you are getting in some healthy fat, unless you don't value your skin and hair.