This combination of symptoms are likely caused by either a viral or bacterial infection. If you also develop a stiff neck, you should reach out to your doctor to discuss the possibility of meningitis. Viral infections generally resolve on their own with time.
While the list below can be considered as a guide to educate yourself about these conditions, this is not a substitute for a diagnosis from a health care provider. There are many other medical conditions that also can be associated with your symptoms and signs. Here are a number of those from MedicineNet:
Indigestion (dyspepsia) can be caused by diseases or conditions that involve the gastrointestinal (GI) tract, and also by some diseases and conditions that do not involve the GI tract. Indigestion can be a chronic condition in which the symptoms fluctuate in frequency and intensity. Signs and symptoms that accompany indigestion include pain in the chest, upper abdominal pain, belching, nausea, bloating, abdominal distention, feeling full after eating only a small portion of food, and rarely, vomiting.
Sinus infection (sinusitis) is caused by allergies, infection, and chemicals or other irritants of sinuses. Signs and symptoms are headache, fever, and facial tenderness, pressure, or pain. Treatments of sinus infections are generally with antibiotics and at times, home remedies.
Meningitis is inflammation of the membranes that cover the spinal cord and brain. Symptoms include fever, headache, and a stiff neck. Treatment of meningitis depends upon the cause of the infection and may include antibiotics or antiviral medications.
At MedicineNet, we believe it is important to take charge of your health through measures such as a living healthy lifestyle, practicing preventative medicine, following a nutrition plan, and getting regular exercise. Understanding your symptoms and signs and educating yourself about health conditions are also a part of living your healthiest life. The links above will provide you with more detailed information on these medical conditions to help you inform yourself about the causes and available treatments for these conditions.