I am a 20 year old female who was diagnosed with fibromayalgia when I was 12, and have suffered from fatigue, headaches, joint pain, and back pain since then, but my doctors have theorized about the possibility of my problems being autoimmune. In the past month I started randomly breaking out into hives, and in the past week it's been happening multiple times a day and I've started to have really liquidy diarrhea for three days now alone with the hives. The hives start in different places each time and there's no common factor in what I do or eat or in my environment. I'm also nauseous and extremely fatigued and lethargic despite plenty of sleep and even with my usual morning coffee. I took an antihistamine and the hives went away hours later but not the diarrhea, and I'm not convinced the antihistamine was even why they went away since it took so long. Are there diseases autoimmune or otherwise that can cause this?