Has anyone checked you for triggerpoints across your upper back and scalenes?
I would start there and then after do some stretching of those areas.

Have you seen the pressure pointer trigger point chart?
It can help to show a friend where to press for TrPs.

But basically if you do have TRPs - you have to get rid of them first - stretching alone doesn't really do it.

You would be stretching a muscle that has an irritated spot - just makes it worse most of the time, untill that TrP is resloved. and other latent TrPs may shopw up, but they all need to be taken care of.