Hi Sva :-)
My first thought is that you're bringing up energetic blockages that were deeply rooted for release.
sickness is, after all, only the body's attempt to restore balance.
regarding the shoulder and neck pain, one of my other masters says that it's very easy to be unconsciously very tense in this area. The shoulders are key to allowing the energy to flow throughout the system, so maybe you could put your attention here when you begin and ensure you're relaxed. Just go back and check throughout the session.
Master Lin also says that any pain that comes up is an opportunity to work through it for release :-)
Many blessings,
Dean
