It's no surprise you didn't have a massive loss as 400cals a day is absolutely nothing and then you add exercise on top of that, your poor body was probably wondering what the hell was going on! I know it is so tempting to want to lose it all so quick, but remember that maintainence is one of the hardest parts. You have done so well so far and you should be so very proud of yourself.
When we ask our bodies to exercise, we need to give it the proper energy it needs to be able to do the things we're asking. It's just like expecting your car will get you from A to B with no fuel in it, you will do damage and it will come to a point where it's just not physically possible.
Love your body for all that it has done and continues to do for you and treat it as it deserves - with nourishing food to get it through the day