I have along haired cat who is always cleaning himself, he does it so often he's licking himself raw. I've tried putting some oil in his food ( heard it's good for dry skin) I heard yeast was good for dry skin as well and tried that to. I check him regularly and have only seen one flea, plus he's not itching he's licking. I feel so bad because of the raw spots, I've thought about shaving him to see if that will help. Any suggestions?

Please take him to a vet. He could have an allergy that you aren't able to deal with. He may need a prescription med or something that only a vet can provide. (Shaving him won't help. That will only make it easier for him to lick himself raw.)

Even if you haven't seen more fleas, that could still be the problem. I have a longhair that started obsessively cleaning, to the point of bald patches, when he got fleas. It's easy for fleas to hide in long fur, so you really should get rid of them.

As WG said, it could be an allergy. Only a vet will be able to tell you, for sure.

Vet and flea treatment seem like the best approach, to me.

Where is your cat licking? Cats will often do this to their abdomen if they have a urinary tract infection.
As mentioned above, a vet is in order as it could be one of many things.

Obsessive grooming is also fairly common, as an obsessive-compulsive disorder. Usually it manifests itself by abdominal grooming to baldness. It tends to be more a problem between the ears than anything physical, so let your vet be the referee here.