I used to sleep for 12 hours regularly for my entire life. After discovering that I am allergic to wheat, and have completely quit eating it, I sleep less.
Get a blood test to look into whether you may have a food allergy (celiac for example).
Additionaly, the airflow through my nose is obstructed, causing me to wake up with a really dry mouth. A couple years ago I started using breath-rite nasal strips to open up my nose so that my breathing through it is unobstructed. Now, if I forget to use a breath-rite overnight I wake up absolutely exhausted due to the lack of airflow.
It is possible that I have sleep apnea when I don't use the nasal strip, but when I have the strip opening up my nose for greatly increased flow I reduce or eliminate the effects.
Look into your diet. Check for allergies. 38% of the people with celiac disease (allergic to wheat gluten) have NO symptoms. I personally get absolutely exhausted after eating wheat- especially waffles or even worse- Panda Express, which has wheat and also soy (which has wheat in it)- plus all the sugar. I would do a blood test for iron because celiac can cause anemia, due to the fact that it kills all the villi in your intestines so that you no longer absorb nutrients and have an allergic reaction to almost everything you eat.
Understand that the food that you buy in a box is man-made from chemicals- garbage God never intended us to eat. If you can't pronounce the words in the ingredient list you should not be putting it into your body.
Eat fruits and vegetables and exercise. Another cause of excess sleeping is depression, but 30 hours of sleep is such a crazy amount of sleep you must have something more serious going on. Maybe anemia? Maybe anemia caused by celiac disease?
Go to a naturopath because they actually look into your whole lifestyle and diet and try to fix you. Medical doctors are only trained to cut things out and prescribe poison pharmaceutical drugs that cause your body ph to become acidic so you get cancer.
An M.D. might give you the celiac blood test if you could convince them that you want it bad enough- then if you have it they'll tell you, "You have celiac, don't at wheat. Also you have IBS. Good luck." Completely worthless.
Go to a naturopath- they cure causes (lifestyle and diet). MDs cover symptoms with toxic drugs and cut things out. It is not their fault- they only know what they are trained.