My 6 Yr Old Cat Has Always Had Problems With

My 6 yr old cat has always had problems with vomiting right after eating, but the last two days has been vomiting 6-8 times (that I know of). Nothing in his vomit like worms or blood, but today I looked in his mouth and his gums and tongue are blue. He was hiding most of the day, but now I have him in a confined area. no new changes in his diet, same dry cat food.