My 5 yr old cat was diagonsed with CRF 2 months ago. Now, he has mouth ulcers..I looked in his mouth..?

and did not like what I saw..the ulcers appear to be on his gums too and one of them causes a little bloody drool....a couple of his teeth dont appear to be in great condition either....PLEASE HELP!! what can I do..I have been giving him slippery elm but that doesnt seem to be helping, it just seems to be getting worse..I cant take it, Im so sad to see him like this..please please any advice?? can i give him anbesol? hes stopped eating and doesnt really drink much either