When you are not used to looking at x rays then it is difficult to be sure of what you are seeing. There are some structures that we expect to see on left hand side (heart for example) and we expect to see the diaphragm at the bottom..
If your lung capacity on the left was reduced then this is determined by lung volume tests unless there is clear evidence of a collapsed lung. Your history could indicate a chest infection or pleural infection but without seeing it is difficult to be precise.
Have a look at this set of slides: here. Do not get too involved in each slide, I just enclose this so you can see what a variation in appearance in x rays that you can see and you do need to wait until your doctor has had a look before you get too worried.
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