There are lots of interesting features here. “You” is unstressed, so can become /jə/. “Could’ve” is, of course “could have” contracted. If it’s easier, you can miss out the /v/. Miss out the d at the end of “told” also, or pronounce it as if you’re beginning to make a /b/, but keep it in and go straight to the /m/.
The phrase means “I’m a bit cross with you because you didn’t tell me something I needed to know.” Plenty of stress on “told”.