It is probably a combination of things. Your vigorous physical activity, (you stud), & exposure to your GF's cold. If you have a fever go to the doctor, even if you get the fever to break with something like tylenol, don't mess around with it. If you don't have a fever play it by ear. Your illness may last a few days, even if you go to a doctor he or she may send you home and tell you to get rest, etc. If the illness lasts for more then a few day, even with out a fever go to the doctor.

Eat good healthy foods, if you can stomach them & keep them down. Juice is ok, but drink lots of water. Stay away from beer & soda pop for the time being. Sports drinks may not be a bad idea too, but not to much at once.