I agree with Opus. He could be stressed but he could be in pain.
Please take him to the vet. I don't think there is anything you can do at home to treat him.
Good Luck.
hi...yes feliway does help with stress. however IMO..excessive licking in the genital area indicates pain. is the cat a male?
they are very prone to urinary tract crystals, their urine than becomes very concentrated and strong smelling too.
kitty needs to see a Vet asap. crystals can be fatal for kitties, I've been dealing with that with my male.
If kitty is on dry food please switch asap to canned(much higher in moisture) will help with the concentrated urine.
and try to get kitty to drink as much as possible.
You could call your vet and discuss it with them; it may be a urinary issue.
If you're fairly sure that it is stress, you might try a feliway diffuser; My Fluffy has been pretty easily stressed for some time, and I use a feliway diffuser all the time. They contain a synthetic calming cat facial pheromone. It can be expensive, but you might only need it for one month. If you go to the petcomfortzone website, I've found a coupon there before. There are different brands; I know my vet's office sells a different one.
Either way, it's probably good to discuss with your vet.