I'm not sure the factor that makes your lips dry is. Here I list the most common situations and the solutions:
1. You probably have been using a lip barrier instead of a lip balm.
There are chances that this barrier contains lots of petroleum, and I won't sanction it if you really wishes to help your dry lips, because it can't do shit. All it ever does is to wrap itself over your lips like a film of sticky thick grease. But it neither adds moisture nor encourages dehydration.
2. You have used drying cosmetics.
Most glosses and lipsticks does this, sadly. Some can be quite terrible. They may have very nice colors and textures, but often leave creases and cracks in your lips after a day. I did apply one of my favorite long-lasting lipsticks to a dinner hosted in my honor a night to my wedding, but it turned out to be a very bad idea because my lip was in a mess on my wedding day, no thanks to the stupid lipstick.
This is not limited to lipsticks. You can often swipe some foundation or BB cream on your lips and it can always leave some damages. It is no longer in vogue to apply some concealer before applying your lip gloss because it only leaves you with more cracks. The better option now is to use a nude pencil or a lip primer.
3. You are dehydrated.
Whenever I develop dry lips from makeup, which happens very often, my makeup artist always scolds me for failing to drink enough water. Your lip is one of the first places you are likely experience cracks when your body does not get enough water. So next time you get a dry lip, check your water consumption. You could have possibly been taking less water than your body requires. Start drinking!
4. The environment wallops you.
Heaters in the winter season, AC in summer, wind, snow, salt, sun, etc., it sees the earth get a fair share in Burt's Bees. The way out is, be prepared always: do more prevention than treatment. So always think about your lips. Use a moisturizing lip balm or barrier if you love using them to protect your lips. Equally use SPF to protect yourself from the sun to avoid getting aged or burnt lips, or at least a cold sore.
5. You lick them often.
For God's sake, you should have some self-restraint. This is like offering a drunken girl more tequila because she feels thirsty. Do not do this.
Wish my words could help you.