What reasons do doctors ask you to come in to see about your blood results? ?

Im 2o years old and I went to the doctors because my neck was a little swollen, I was fatigue, sore throat, headache, mild fever and was spitting up mucus for about a week in a half..I heard on the news that alot people have been getting the flu but im pretty nervous cause I had the doctor do a regular blood test CBC, CMP, some other routine test and thyroid...im so scared cause I was told to come in and all the symtoms I had were really scary diseases like hiv:/