My Cat Has Not Been Acting Like Himself Lately. He Is Normally Very Playful And Loving. It Started Out A Week Ago When I Noticed He Was Vomiting, That Has Since Stopped. Now All He Does Walk Around The House Very Somber And Drink Water.?

If your cat is vomiting for even just one day, it  is serious.  Cats cannot go without food for more than a couple of  days because it will destroy their liver. Dehydration alone can be fatal, as well.  Just drinking water is   usually not going to be enough to rehydrate a sick kitty. The runny nose is cause for concern... Only a vet could try to figure it out through blood  samples,  Ask yourself this: Is kitty currently up to date with vaccinations?
A runny nose could be a symptom of FLV. Vomiting can be anything from  toxicity, infection, obstruction, virus or even cancer. Hurry if your pet means something to you.

If there are  real plants in the house and the cat eats it and is not quite use to it they usually vomit... :)

Your cat has diabetes. My cat did the same things. He is on insulin now.