I have terrible sour stomach please help!

I have really bad sour stomach which I get almost everytime I eat. It feels like I have an excess of acid but when I take any kind of acid reducer (alka-seltzer, tums, Pepcid AC) they don't have any effect. It makes my stomach always full and I'm never hungry. I have had this for several years now. Please give me advice on how to treat this!