Do I have a cold or is it allergies or could it be the flu?

I live in Washington and I went to Missouri for a family reunion. On the day I went back home, I had a really runny nose and it was clear mucus. The next day, I woke up and I was really achy and congested. yesterday, I woke up and I was less achy but blowing my nose regularly and coughing. Today I was coughing up a pastel yellow kind of mucus and I have a fever along with the chills. What do I have?