OK First off I agree that it sounds like you have a recurring pilonidal cyst and it may be infected, and, if so, that could be causing some of your symptoms.
The other expert mentioned mononucleosis and I agree that can cause the symptoms you're having.
But in addition to all that there are other possibilities like anemia, low thyroid, vitamin B12 or vitamin D deficiencies, and an autoimmune disorder like polymyalgia or rheumatoid arthritis.
You basically need to see a doctor for an exam and testing which should include a CBC, metabolic panel, mono spot test, and an autoimmune screening with antinuclear antibody, rheumatoid factor, sed rate, and C reactive protein
Of course the pilonidal cyst also needs to be addressed