What Causes Lower Abdominal Pain?

Hi,I all of a sudden had pretty severe pain in my R lower abdomen above my belt line, with pain in my R frt neck down under my collar bone. Now it has gone down my R arm some. Worse if I breath fully, way worse if I lay down. Has been like this for 8 hrs now. Didn't do anything strenuous to be muscular.
48 yr old male on BP and cancer med.
Any idea