I’m hardly eating anything and when I do I feel nauseous?

Hi, I am a female age 23. My name is (…), I am currently taking no medications but I do have a Nexplanon birth control implant in my left arm.

I have been feeling very ill lately, and it usually gets worse if I eat. I do feel hungry, but can only eat a few bites and then I feel sick. Recently its been getting worse, I’m hardly eating anything and when I do I feel nauseous but I also started feeling a burning pain in my lower back, shoulders, neck and even in my jaw. Its almost like a tightness, but its hot and hurts. It was really bad today to the point I almost passed out. The pain usually lasts 15-30min and then goes away and then I just feel nauseous.