My dog is gagging like he is trying to spit up somethng and nothing comes up, I s there something I can give him to help...

It may be allergies. I am not quite sure exactly what your dogs gagging sounds like to know for sure but when my dog is in the yard she does a gagging type sound from the grass or pollen.

What kind of dog is he?
Is he gagging, or retching?

Give water. Rub her upper tummy or her throat. This type of thing happens to my dog as well. Not that it helps the gagging but it helps her to relax.

Gagging or coughing can be a symptom of many things, tonsilitis, kennel cough, heart murmurs... if she doesn't stop the coughing in the next 24-48 hours (depending on severity of the coughing) she needs to be seen to by a vet.

I know this is an older thread, but I just found out that my dog has a heart Murmur, and coughing is one of the symptoms, mainly coughing after they have been resting or sleeping. Could it be a reverse sneeze? Depending on the dog his/her pallat may be longer then normal, and when they do the reverse sneeze it will irritate the pallate and it then becomes swollen and they gag. Normally not an issue uless it interfers with their eating or breathing, or they are CONSTANTLY doing it.