Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am sorry to hear that your little one Papas has had several episodes of dry heaving.
Dry heaving and nausea can be due to stress, a change in diet, parasites, a viral or bacterial infection, eating something he should not (like a piece of a toy or string), inflammatory bowel disease or even a food allergy, or heartworm disease. But it can also be related to metabolic organ disease (such kidney or liver disease) due to organ wastes irritating the gut or an obstruction in the gastrointestinal tract.
Some cats that are big gobblers when eating, especially of dry food, can overeat or swallow lots of air and that can lead to retching/dry heaves.
Please check the litter box to make sure that there are the normal amounts of urine being passed. Male cats can get urethral obstructions due to inflammation, mucous and crystal formation. If they cannot urinate they quickly go into kidney failure due to back-pressure on the kidneys from being unable to urinate and that can cause vomiting and abdominal pain. If he is quite uncomfortable with abdominal pressure, has been back and forth to the litter box several times today, and you cannot tell whether he is urinating normally today an emergency veterinary visit is best.
But if he can urinate fine then there are some things we can do to try and settle his stomach.
To try and settle his stomach today you can try either:
1) Pepcid-ac (famotidine) at a dose of one quarter of a 10mg tablet per 5 to 10 pounds of body weight every 12 hours.
2) Prilosec (omeprazole) at a dose of one quarter of a 10mg tablet per 5 to 10 pounds of body weight every 24 hours.
These will reduce stomach acid and should help if this is related to simple nausea and gastrointestinal irritation.
I would wait to feed him any food for a good 6-12 hours after the acid reducers are started. This should help stop gut spasms and restore normal gut motility. Small amounts of water or clear broths like low salt chicken broth offered frequently are fine as he needs fluids. You can give him pedialyte to replace electrolytes too, though most cats don't like the taste.
After his food fast offer him a bland diet mix of 2/3 boiled, white skinless chicken, all fats and juices drained off the meat, mixed with 1/3 boiled, plain white rice. Feed several small meals a day.
Once he feels better (no retching for 48 hours) start mixing in his regular cat food very slowly, less bland more regular with each day. It should take a week or so to convert him back. You might try feeding him canned only food as his regular diet and see if that helps.
If he eats very fast there are bowls designed to slow down eating. See this link for some examples: https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=cat+bowl+for+fast+eaters&tbm=shop
If Papas is continuing to retch, runs a fever or has a tense painful abdomen and is feeling poorly though it would be best that he see a veterinarian now.
Best of luck with Papas, please let me know if you have any further questions.