Maine **** aging... me worried

My maine ****, Tangerine is the first pet I ever had.

I paid 5 dollars for him thru a local newspaper want-ad.

I was dating a girl I worked with when I adopted him ( he was 2 months old).

Now it is 15 years later, no longer kids, & Tangerine is having a hard time breathing.

We used to take him to the vet for shots & to get fixed.

However , we were young ( and now married) and are embarrassed that he has not seen a vet for the past 7 yrs.

I feel like we HAVE to take Tang to the vet , but my wife is convinced that he is not suffering and if we take him they will put him down.

He has lost a lot of weight.

Maine **** cats are big- he has been big all of his life, but now I can see his lungs working and heart beating thru his fur.

He hardly has an appetite.

This has been going on for approx 6 months.

Help....
Please--

This is the first pet I have ever had.