What Causes Chronic Fatigue Along With Alternating Constipation And Diarrhoea?

I am very frustrated. I have had multiple blood tests, and seen many doctors. No one can figure out what is wrong with me. I am ready to give up. I am a 46 active female. I have been very athletic my whole life. In the past 2 years my health has gone down hill. Doctors just keep putting me on antibiotics, so in the past 2 years I have been on antibiotics every other month. My symptoms are chronic fatigue, skin ulcers, chronic diarrhea, or horrible constipation, physical activity such a a hike or swimming laps leaves me the next day feeling horrible muscle aches so bad I can hardly move. Other symptoms include, sinus congestion, and I am prone to infection. This is not normal. ESPECIALLY the SKIN Sores. They last for at least 2 months. Can someone please help me. I am ready to give up I think it is celeac disease and has damaged my small intestines in some way.