I have discomfort on the left side of the chest, not really a pain, its been going on for 3 weeks now.

Need more info: Chest discomfort can be due to many reasons. If it is mild, not getting worse, then it may be due to muscular sprain or injury of some kind. This should get better and go away in a week or two. If this is getting worse over 3-4 weeks, then a medical examination by your doctor would be indicated. A chest X-ray may be the first useful test. Further testing will depend on the results of initial test