What Causes Diaphragm Spasms And Heart Palpitations?

I am having spasms of the diaphram which make my heart race and makes it difficult to breath. I have not been able to get any answers from my Doctors. I am presently taking Lorazipam 5mg twice a day. These spasms never really stop they go on 24hrs a day at times severe other times milder but never stop. How can I find out what is causing this . This has been continuous for about six weeks.