If you are really unwell and don't feel up to exercising, doing some stretches can be the next best thing. Particularly stretches that focus on the muscles around the chest area, which can get very tight from constant coughing. It also gives the body a chance to get some circulation happening, and some of the harder stretches can make you breathe deeply.
Some stretches I find useful are.......
Find a doorway. Raise your arms above your head (if you're a shorty you might need to stand on your tippy toes!!) and hold the top of the doorway with your hands. Pull forward and you should feel your back and chest stretch. Or, put your arms to the side of the doorway, and again holding on with your hands, pull forward and you should feel the back of your shoulder region get a good stretch.
To loosen the back of your neck, let your chin drop forward to your chest. Place your hands on the back of your head, and gently put some pressure on, until you feel the neck stretching. Do this a couple of times.
Rolling your neck clockwise and anti clockwise and side to side very gently.
Swinging your arms in a circle, one by one and then together, forwards and backwards.
Hunching the shoulders up, then dropping, repeating this several times.
To stretch the torso, get a solid chair. Lie down on your back over the chair, and with your feet on the floor - let your head, shoulders and chest hang over one side of the chair, and you should feel the front of your body stretch and lengthen. I love this exercise.
Repeat this exercise, except lie on your side, and then swap to the other side. This helps to stretch the muscles over the ribs. Raising one arm over the head also increases this stretch.