Left arm and pain. Any advice?

I have been having pains across my upper back on the left side and it goes across the chest and down my arm and pains real bad then goes away. My blood pressure is normal I think . I am on blood pressure medicine .So when it happens and not often and I do have breast cyst on that side under my arm that when Examined hurt . Could it be from that ? It takes a bit for me to even move my left arm from the pain even across the back part under the arm .Not all the time only if I move my arm a certain way then the attack comes on any info would help.