What symptoms are these symptoms of?

I've been coughing for weeks, and it has gotten only slightly worse over time. My nose became congested only about a week ago. If I were sluggish, I probably wouldn't know it, because that's just how I am most of the time. My bro and his GF both had some sort of sickness that caused them to have similar symptoms, but they were also vomiting, but I have not vomited and have felt no nausea. So maybe it's a common cold? Maybe. I would think otherwise because of the time-span. Maybe it's the flu? Maybe. I have always been good at avoiding vomiting. So what could it be, and should I be worried?