Hello, my name is Dr. Kara and I have over 20 years of experience as a veterinarian.
I'm sorry to see that you have been waiting a while for an answer and I'd like to try to help if you still need some recommendations but I do need more information from you.
How old is your kitty?
Has he had any previous health concerns? If yes what were they and is he currently taking any medications?
Is he straining and passing small amounts of very hard, dry stool? If yes, how long has this been going on?
Any other episodes of vomiting, or just the one episode?
Is he urinating normally?
Is he eating still?
Is he drinking water?
Are you able to take a rectal temperature? A normal temperature in cats is 100F to 102.5F.
Constipation can be a primary problem, especially in older cats with poor intestinal motility, but it is more commonly seen due to dehydration, organ failure or eating a foreign body. If you can tell me what else is going on with him then I can give more pointed recommendations. Cats that are obstipated however, unable to pass any stools at all need hands on veterinary care and if he is vomiting all that he eats and refusing to eat that may be the case with him. Please let me know if you still need help.