My mom thinks I'm developing anorexia, but I'm not sure.

Okay so I'm 16 and I've never considered myself to be skinny; I have a really bad personal self image- but everyone else thinks I am. I think right now I way about 105, and I'm 5'3. So this summer my aunt died and it really upset me, and I just stopped eating as much so I lost like 20 pounds over a month period. I have continued to loose weight, but I still feel heavy. Now my mom's worried because she can see my ribs and my hip bones and part of my spinal cord. I just don't feel like eating; food just lost its appeal to me. I have also noticed that since I lost all the weight my stress level has gone down. I don't know if I'm anorexic or not, but I don't want to worry my mom. If I am what should I do?