Very bad stomach. And irritation.

I've stomach problem and I've searched for this on the net and found this as GERD.Except fruits eating anything makes my stomach heavy, heartburns, gas and hot liquid coming back into mouth etc and whenever I'm having this it gives me burning eyes, headache, fluish and concentration loss.it's very irritating as it's involving with my daily life some of the foods I'm having the problem with are masala items, red chilli powder, citrus fruits, chocolates, biscuits, ice cream, medicines etc. so I've completely avoided these and eating normal curries without chilli powder and avoided all processed food. even though taking very light food making me feel like having heavy stomach and gas formation. and I'm having a very very less appetite comparing to my friends of the same age. I can stay a day long without eating.the only time I feel like having happy stomach is after good defecation. if I had bad defecation like some left undefeated, I'll have the worst day with a headache and irritation.