I was laying on left side and felt a small brief heart pause like of needing to catch breath. i feel ok now..sitting up. what could that been?

A skipped or : delayed beat is not uncommon.If it makes you sick like dizzy,short of breath,weak,lose consciousness,notify your MD

PVC: A single flip flop like that is caused by a premature heart beat triggered outside the normal pacemaker. This causes reset of pacemaker and a pause. When heart re-fires on schedule, extra blood collected in pumping chamber causes a larger than usual beat which is felt as a thump. Sometimes several of these can occur. If there are no other symptoms they are benign.