Since February 2015 I,ve Been Having What I Thought Is

Since February 2015 I,ve been having what I thought is breathing problems.If I exert myself I would get a headache, my stomach would feel like its being squeezed,and my throat would feel like someone is squeezing it ,then I would experience immediate fatigue and I would be really short of breath.The fatigue is mainly in my chest, my legs and arms aren,t tired.At night when I lay down I feel my throat is being squeezed and I have a hard time breathing after a while I would sit up and my breathing is better I would have to do this maybe 2-3 times before I can lay down and breath well then go to sleep.
Since the past 2 weeks I have bought over the counter drug called Zantac and have been better but the symtoms are basically still with me with exception of my sleeping problem its basically good.I do not have chest pains the only pains I have in this region is once in a while a pain on the top of my right shoulder[collar bone area]