Hello I would recommend when getting ready to go to bed to take Vaseline and glob it on your mouth and any reddened surrounding areas, and sleep like that. Do Not uses directly over nose holes because you can suck it into your lungs.
During the day use and reapply Chap Stick- the blue raspberry smells and tastes the best, frequently. Then Repeat the Vaseline at night.
There are things you can get at Wal-Mart, etc called Udder Butter-comes in a small green tin can (this is used by farmers when the cows udders become severely chapped from milking, this works great on lips, dry scaly patches, severely chapped hands, and for use on new tattoos, too ), or zinc oxide, either should do the trick but both smell and taste really nasty, so only use at night when you are less likely to lick your lips.
If this doesn't stop the problem within a day or 2 it is most likely being caused by something else like Yeast, dermatitis, or a vitamin B or iron deficiency, or a reaction to a medication you are taking etc., and the doctor will need to again check you to determine which one is cause. I Hope This Helps!
Are you drinking enough water? If you are somewhat dehydrated that can cause it also.
Make sure you are not licking your lips.
You can try vaseline. I also think Blistex lip balm works quite well, as does coconut oil.
If it is cold where you are, use chapstick lip balm for protection before walking out in it.