If you are vomiting blood(frank or dark) and having dark tar like stools(blood that has made its way through the g.i. tract and metabolized) it sounds like it may be suggestive of a G.I. bleed. Given your symptoms and that you've been previously diagnosed with a hiatal hernia and reflux disease this leads me to believe it's probably an upper G.I. issue. I would definately get in to see your doctor asap for an evaluation. I'm sure they are going to run a battery of tests and most likely want to do another endoscopy to assess for a possible bleeding ulceration. I wouldn't get all worked up though as it could be a number of things.