What Causes Rapid Weight Loss Along With Stomach Cramps And Joint Pain?

What causes rapid weight loss, stomach cramps, joint pain, nausea, delayed periods, rectum pain, fever, chills, no appetite, light-headaches, swollen stomach, headaches, muscle spasms/shakes, etc? I have had all of these symptoms and gain more everyday. Two months into feeling sick and I've lost over a pant size and losing weight daily.