Yes, you need more calories. The very best formula/simulator I have found for caloric needs in a weight loss program was put together by Dr. Chow of MIT and the NIH. Here is the link:
http://bwsimulator.niddk.nih.gov
You will have to download or update Java to use it.
If you eat too little, your metabolism will slow down and you will find it more difficult to lose weight.