I am sorry your kitty is not feeling well. I suspect that your cat has a systemic illness that is causing his difficulty. The lip smacking and licking you are seeing are signs of nausea and the abdominal discomfort can be due to gas, constipation or dehydration. Cats are considered to be geriatric at 8 years old and are prone to illness as they age. The 3 most common ailments known to afflict elderly cats are diabetes, kidney disease and hyperthyroidism. The symptoms include vomiting, diarrhea, increased water consumption, increased urination, dehydration, weakness, weight loss, poor hair coat, changes in appetite, changes in behavior and increased vocalizations. Cats instinctively hide illness, and can be pretty sick by the time their people realize something is wrong, and I am worried that your kitty is exhibiting obvious symptoms. Cancer is also a possibility and a tumor can explain the discomfort in the abdomen. Your kitty could also be arthritic and that can also explain abdominal discomfort.
I think it would be a very good idea to have your kitty seen by his vet tomorrow for an exam and some bloodwork. Most vets have very limited weekend hours, and I worry that your kitty will get very sick while your vet is closed. I do not want you to have to take him to an emergency hospital if you can avoid it. Please let me know if I can be of further assistance. If this has been helpful, please hit the green accept button. Good luck, let me know how your kitty does.