Have had a severe respiratory infection for four days now it has now moved to my chest and is very tight is it time for antibiotics...

Probably won't help. Most problems like this are due to viruses and antibiotics won't help. If the chest symptoms continue more than a week, or if you start coughing up large amounts of colored sputum, maybe an antibiotic would help. But usually not for shorter illnesses like yours. But check with your doctor to be safe.