Sounds to me your body is trying to clear years worth of accumulated tar and gunk from your lungs, that's not uncommon.
There could conceivably be irritation from sub ohming, how low are your ohms and how high is your nic level?
Another consideration would be a flavoring that might not be sitting well with you and causing irritation.
My guess would be the first but it wouldn't be a bad idea to see the Doc to be sure.
Welcome to the forum and congratulations on a new, non smoking, chapter of your life!