Even though one may not feel anxious, the brain can still behave as if you are anxious. Some of the twitching can be this non-emotional anxiety. The brain does some strange things that don't appear to make any sense.

Other symptoms are the result of healing. As a system heals, its dysfunction changes to a different stage in the healing process. When nerves are injured and start to heal, at first there may be numbness, then as they start to reconnect, they tingle, twitch and may have needle stick like feelings. The brain's nervous tissue goes through the same kind of stages.

You shortness of breath when laying down may be a result of you momentarily not breathing. It could be a muscle tension that causes you to hold your breath without knowing it or it could be an apnea where your brain stops telling your diaphragm to take a breath. Then as your brain recognized the need for oxygen, you start to breath harder as you feel short of breath.

Have you had any diagnostics or therapy for your upper back and neck ? You may have a rib that is partially dislocated where it 'plugs' into a socket at the vertebra. This can cause the chest pain. A dislocation at the back end of a rib will manifest pain or discomfort at the sternum end of that same rib. Spending too much time on the couch or propped up in bed can be a problem for a dislocated rib.

It might help to read the neck exercise post by sleepybo or get some advice on how to stretch and limber up from a trainer or PT.