How Can Chapped Lips Be Treated?

hi i'm suffering from severe chapped lips for over 3 years now and my GP and doctor have failed to help. i recently discovered it was most likely due to the fact my nasal passages were blocked and it was causing me to drool in my sleep which would lead to my lips being cracked and peeled in the morning. This is a regular occurrence that happens every day and night, my avamys nasal spray didn't help and i don't know what else to do. And yes I've seen my local GP, Doctor, ENT doctor too.