Typically, the symptoms of a true influenza infection last about 7-10 days, though they can last up to two weeks in some people. The fever generally doesn't last as long... usually only 2-5 days. Other symptoms include things like fever, headache, dry cough, congestion, fatigue, aches and pains, breathlessness, poor appetite, and even nausea and vomiting in some individuals. Over the counter medications don't help you get over the infection faster and only work to relieve some of the symptoms... such as tylenol for fever and aches and pains. If you've had the symptoms for less than 48 hours, your doctor can prescribe antiviral medications that may help you get over the illness more quickly and with less intense symptoms, such as Tamiflu.
Many people confuse the flu with the common cold, as they both have upper respiratory symptoms. If your symptoms came on quickly and you have a high fever, chills, and body ache, it's more likely to be the flu. If you're not feeling quite as bad and just have some congestion and fever, it may be a cold. Colds last about as long as the flu, but are far less intense. Keep in mind that if you do take Tamiflu, it will only work if you have the influenza virus, as it doesn't work against the viruses that cause the common cold.
In most cases, both a cold and the flu are treated with plenty of fluids, rest, and symptomatic relief. For a fever, try tylenol every 4-6 hours and/or ibuprofen every 6-8 hours, wearing a single layer of clothing to stay cool (but not cold), and lukewarm baths. If you can't manage the fever with over-the-counter remedies, or it gets higher than 103.7, you should seek medical attention. For other symptoms, "cold and flu" variety of medications may help. Be sure, if you are taking tylenol or ibuprofen, to read what medications are in "cold and flu" combination medications before taking it. Many of them have tylenol or ibuprofen already in them, and you wouldn't want to double up on tylenol by also taking it separately.
I hope this helps, and hope you feel better soon!