Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am very sorry to hear about your pup's panting, licking, and eating grass.
I don't think that your pup is in a bloat situation yet, because he is still able to eat things and swallow, although he may progress to that.
If he attempting to vomit but unable to do so, his belly looks more distended and very tight, or he won't lay down and settle, or he is pawing at his mouth or staggering, then I recommend he see a veterinarian immediately as those can be a signs of bloat, a rare occurrence but life threatening if allowed to progress.
I do think he is feeling very nauseous. Dogs with nausea or gastroesophageal acid reflux often lick repeatedly, and eat grass or foreign material to make themselves vomit. They will often swallow repeatedly and lick things trying to soothe their nausea and acid burn. If they can rid themselves of whatever is irritating their stomach that way then all is good. But when they continue to be uncomfortable then we need to stop them from eating any more grass. It becomes a vicious cycle where the more grass they eat the more their stomach gets irritated, their stomach acid refluxes and burns their esophagus and the worse they feel.
Possible causes of nausea causing grass eating include a change in diet, dietary sensitivities or allergies, or eating things that they should not like too many fatty table scraps or garbage, bones etc. Addison's which is a poorly functioning adrenal gland is another possibility for waxing and waning vomiting and nausea. Metabolic organ failures (kidney or liver disease), pancreatitis, inflammatory bowel disease or even infiltrative cancers are possible causes too.
Has he eaten anything he should not have recently (toy pieces, bones, garbage)?
Any changes in food or treats?
As long as his abdomen isn't quickly enlarging and he isn't trying to vomit repeatedly unsuccessfully then we can try some things at home.
To try and soothe his stomach and decrease nausea you can give him acid reducers to try and settle his stomach.
1) Pepcid-ac (famotidine) at a dose of one 10mg tablet per 20 to 40 pounds of body weight every 12 hours.
2) Prilosec (omeprazole) at a dose of one 20mg tablet per 40 to 80 pounds of body weight every 24 hours.
These will reduce stomach acid and should help settle his stomach. These can be used for several days if necessary as they are very safe.
I'd also pick up his food and water for now. A couple hours after giving one of the acid reducers you can offer small amounts of water or ice cubes to lick. No food for 24 hours. Small amounts of water only.
After his 24 hour food fast then start a bland diet of 1/3 boiled, lean hamburger (or boiled, white, skinless chicken) and 2/3 boiled white rice. Give small meals several times a day. Feed the bland diet for several days, and if all is going well then then start mixing in his regular diet and slowly convert him back.
If his vomiting continues then he may need injectable medication from his veterinarian to get his stomach upset under control.
So watch him for vomiting even with the acid reducers, blood in his stool or vomit or a fever (more than 103.5F rectally), a tense painful belly or lack of appetite after his food fast. If any of those occur it is time to seek hands on veterinary care.
Please let me know if you have any further questions.