Babies with reflux can continue to spit up until they are over a year old. I totally sympathize with your question, because my 6 month old has reflux and spits up constantly too. I don't have any great advice for stopping the spitup. I do all the positional things (hold him upright, etc) and it doesn't really help my son either. One thing that does help, but that is frustrating to me, is this advice - feed the baby half as much, twice as often. So if you normally give him 5 ounces every 4 hours, try giving him 3 ounces every 2 hours. It's time consuming, but it's the only thing I've found that helps at all.
The bigger questions are - is your son gaining weight and growing well? And is he fussy? Does he cry after he spits up? Does he refuse to eat?
If he's gaining weight, then he's obviously keeping enough down to grow and that's a good thing. If he's fussy after he spits up or if he refuses to eat, then he may need an acid reducer to keep the acid from giving him constant heartburn. You'll need to tell your ped about this, because you'll need a prescription.
One more possibility - some babies spit up because of a cow's milk allergy. If you haven't already, you could try a non-milk based formula (Nutramigen by Enfamil or Alimentum by Similac) if you formula feed. If you breastfeed, you could try avoiding any dairy in your diet for 2 weeks to see if it helps.