Whenever I lay down I have this bitter taste in my mouth, especially in the morning. But it can happen just by laying down, not even asleep, just not as bad as morning. What could this be? Coud this be acid reflux? I don't have heartburn.

It's pretty possible that you do have acid reflux. A lot of people don't feel heartburn. What could be happening is when you are laying down, the acid is coming back up through your throat. You should get checked to see if the muscle that closes the stomach, ( I always blank on the name, LES or something it's called) isn't closing right.