Dear Shawty Cat:
Relax. (We don't want that new little one to pop out too soon.) Cheese is just another food, and should be enjoyed, not cause for alarm.
What gets sold in the supermarket as "brie" can range from the real thing (food for the gods) down to, yes, pencil-erasers. the hallmarks of a good brie are just as Jim and everyone else said:
-- Ripe, which means on the soft side, maybe a little oozy, but not totally liquid. It also means having a slightly pungent smell, but definitely NOT smelling like ammonia!
-- Pale to light golden yellow on the inside, with a white slightly (only slightly!) fuzzy skin on the outside. That skin is edible. If it is grayish, the inside is probably over-ripe (ammonia alert!) and you don't want to eat it. Period.
-- NOT blue! As mentioned, Saga is a lot like brie, but with mold injected. If it was called "brie" but it's blue, something is wrong! Well, probably, not anything that will hurt you, but just pass it along to your hubby to eat (actually, it would be good melted on some portabello caps as a mushroom-cheese burger).
The main thing is, to paraphrase Duke Ellington, "If it tastes good, it IS good." My favorite way to eat brie is to let it come to room temperature and get kind of soft, then slather it on some good French or Italian bread and eat it with a cut-up pear. It's that simple. (I'm assuming you're skipping the wine these days.) If it tastes too strange to you, or smells really ugly, it will not be a sin to dump it.
As for a "cheesemonger" -- look around your area for a supermarket like Whole Foods, or a fancy specialty store. The prices won't actually be that much higher, but more important, there will be people there who KNOW SOMETHING about what cheese should and should not be. It always helps to buy from somebody who knows what they're selling!
Cheese is just another of life's great pleasures to be enjoyed (in moderation, of course; and in spite of what Markdchef might say!);)
(Sorry to run on so long, but it's after dinner and we split a bottle of Sangiovese from the Finger Lakes. hic :blush: )