The swelling you have described that is felt behind the ear is probably enlarged Lymph nodes as it occurs in a Lymph node region.
Following infection Lymph nodes become enlarged, painful and tender.
After treatment of infection with adequate course of antibiotics, they should regress in size but never to normal size.
Hence nodes that continue to grow in size are significant and those that regress in size tend to be more reassuring. Thus serial clinical examination is essential.
The general symptoms you have described as malaise, muscle pain are non specific and can be symptoms of many conditions including flu.
I advise you to follow up with your doctor.
Keep us updated.
This answer does not substitute for direct medical consultation.
Dr. Safaa Mahmoud.
MB BCh, MSc Internal Medicine. MD Medical Oncology.
PhD Experimental Medicine and Biochemical Science.