"You'd expect" = you would expect. "You'd expected" = you had expected. It's not possible to confuse the verb forms that come after would and had. We pay attention to the verb after the 'd.

Here "you'd" means "you would". "Would" in this example is used to talk about what someone thought.

The "you'd" in this sentence means "you would". but you'd can also mean you had

It's a contraction of you would.

'd will never be an abbreviation for "could". The options are "had" or "would", and as Peachey said, you can tell which is meant from the form of the verb that follows. Many sentences that include "you would" or "you'd" would also be valid sentences with "could"— but the meaning is not identical.