Extremely Chaped Lips!?

Now - My lips aren't just normal ''chaped'',the problem Is that they get so dry,That they start to bleed!It's been going on for a while,I have tried everything there is to try,Carmex,Burts Bees,Nivea Moisturizer and much more!Absoulotely nothing works,they are very dry,cracked,& start to bleed.What would you suggest?