Showed symptoms of a cold, had cough with phlegm, pressure in head.now all i have is headache, weakness, and a mild cough slightly short of breath. help?

Go see your doctor: Most colds are viral in nature. In other words, they won't respond to antibiotics. However, shortness of breath shouldn't be ignored. While this may be reactive airway disease (variant of asthma), you'll need to go see your doctor for diagnosis ; management (inhalers). Headache ; weakness (where?) can be a sign of not getting enough oxygen (or other condition). So don't delay. Go see your doc!