What am I having?

For the past one week i had noticed increase production of mucus . The mucus is yellowish most of the time and only twie its yellow  green in colour. I had been feeling tired also. Yesterday, i experienced headache lasting for one hour. I felt feverish but not sure if i had fever or not. I also had blocked nose. I feel sleepy all the time and had poor concentration.I had occasional cough but not to my attention. What am I having? is it a common cold or respiratory tract infection? Do i need to see the doctor? i am still contemplating  of visiting a doctor.