15 year old cat losing weight fast. need help

Hello. I have a 15 year old cat that is still very active and loves to play. The only problem is he no longer eats dry food and you can feel every bone in his body. It's heart breaking to pick him up and pet him. I'm afraid I'm going to hurt him. My family and I are afraid to take him to the doctor. We have already lost 2 cats in the past 3 years due to sudden illness. I can't bear to lose another one. Any suggestions? Any ideas how to help him put on some weight. I'm truly desperate. Thank you so much for any suggestions.

Just to add some more information. Compared to the other cats we have lost he is not showing any of their symptoms. He drinks water like normal. Not excessively and he doesn't avoid it. He doesn't hide, he loves to lay in your lap and cuddle and he is not having any problems with his coordnation. My other 2 cats were lost to hyperthyroidism and the other to cancer that was all through his body.

What is he eating?   Does he eat wet food?

All he eats is wet food. He was eating dry up until about a month ago. I'm not sure if I can add some kind of supplement to help him gain weight.

How much wet food is he eating daily?   Wet food is much much healthier for cats.    Check out the links the top of this forum for what to feed cats.

Many folks here use 
Its a great supplement to entice their kitties to eat.   I recommend reading some of the reviews on Amazon. 

I know you're afraid to take him to vet out of fear of the news but its better to find out if there's an issue so that you can possibly help him

If he eats all his wet food, feed more of it. Feed it instead of dry if he no longer wants dry. He is not consuming enough calories. He should be offered 9 oz a day. He might not be able to chew. Buy larger cans of canned for him, but please take him to the vet to get checked.

Hyperthyroidism is very common in senior kitties.  I know you are afraid of taking him to the vet but he does need to be checked.

He's now on 3 cans a day. Hoping that might help. Thank you for the link/ information.

I know I'm going to have to. But honestly I've had enough bad news in the past 2 years. I'm truly afraid of anymore. And I know it would devistate my mother. I suppose I'll be taking him sometime this week and hoping for the best. Hopefully it's just a tooth ache.

If the vet finds nothing wrong but old age, you would be very relieved. My 13 year old was negative for hyperthyroidism, diabetes, kidney and liver problems and that helped me tremendously. Even though the blood tests were pricey, they were priceless on one regard. They sell a tube of high calorie treat on Amazon , I just started using it so I'll keep people posted on how it goes. I've been tempting him with high calorie treats too, even bacon, I want to get some weight back on him. I pray every thing goes well for you, all the luck!