It's not unusual for smoking to become unpleasant at times. It's a burnout syndrome which occurs after prolonged use. You've done the right thing by stopping. I recommend you lay off for at least a month or more. Perhaps you're under more pressure than you used to be. Job and other responsibilities can make getting high less enjoyable and smoking adds to your stress rather than relieving it (thanks to paranoia and guilt).
If stress is a major factor in you life then you need to deal with it,
rather than try to mask it with mj or alcohol (I'm not saying you do it,
just that it's not a good thing). As far as your overall health goes,
perhaps it's time for a checkup. As we age we go through physical changes,
and smoking certainly isn't good for our health. Some people are more
sensitive to smoke and you might be one.
In any case it's always good to give ourselves a "breather" from smoke and let our body recuperate. It's nice to get another view of life now and then (remember - that's why we smoke in the first place!). Respect the herb, and respect yourself and everything will work out.
Peace,
The Old Hippy.