Excessive sweating is not characteristic of chronic obstructive pulmonary disease (COPD) or of low oxygen levels, whatever the cause. Sweating does occur with a number of conditions, most commonly with diabetes but also with some infectious diseases. You should see your doctor and get his/her opinion. You should also ask that your oxygen level be checked.
Now that you have quit smoking for a second time, I hope that you will never smoke again. You should also be using inhaled medicine for your COPD. It is always possible that a given medicine could cause sweating.