ASH ~ not really sure this has anything to do with BIPOLAR DISORDER really (I am a Social Worker). I would recommend that you plan your meals out, writing them down and stick to the plan; and don't skip any meals. Don't go by your feelings; as feelings can go up and down, and all around ... as you probably already know.
About the exercise, maybe you can break it up into 2 or 3 smaller sessions a day, but if you want to do it all at once in the morning, I don't see why you can't. You can also try to do some walking during the day; like at school and housework counts too.
Sometimes we eat out of habit, but maybe your body needs a good daily vitamin with minerals to make sure that you are getting all the nutrients you need, esp is you have not been eating at regular times. Also try to make sure that you eat a balanced diet and drink some water each day.
Hope this helps a bit ... Rosebud