Understanding clothing cuts is critical. Few clothes are made for men with athletic builds, with or without the belly.
I have to buy big and tall dress shirts, for example, but department stores don't carry neck sizes over 18, so I have to go to Men's Warehouse. The problem with having an 18+ neck is the clothiers then make the torso a tent because they expect you to be shaped like a balloon.
So, I have found that I have to buy slim fit as those shirts are tapered more, like my own torso. So, a slim fit 18.5 36/37 shirt isn't tight, it fits me like a 15 33/34 would fit a regular sized guy.
Moral of the story is: Try on everything before you purchase for fit and buy the size and cut the fits the best, even if it doesn't seem like what you should wear.
Complication makes it easy to explain failure.