Hello
Severe pain in the left abdomen from last 3 years  may be due to these possibilities , these includes.
1 The first possibility is of 
Peptic ulcer disease or 
Hiatus hernia. Diagnosis can be confirmed by upper G. I. endoscopy. Try raising the head of your bed about 4 inches with blocks. It also might help to avoid eating or drinking for 2 hours before you lie down. To control stomach acid one should not drink alcohol or drinks with caffeine in them or eat chocolates or spicy or greasy foods . Also take some antacid but in your case symptoms are ( as severe pain ) you may need drugs like 
proton pump inhibitors like pantaloc-D twice in day. 
When such patient visit I usually prescribe them to take "REBAMIPIDE" 100 mg thrice in day for 4-6 months . 
2 . The 2nd possibility is of 
pancreatitis as it may cause upper left 
abdominal pain ,which is  worse when bending over or sitting. Pancreatic enzymes like serum amylase & lipase should be measured to rule out any pancreatic cause.
3 The last possibility is of any kidney stones which may present such 
sharp pain radiating to back. For this purpose you need to get ultrasound abdomen .I suggest you consult a physician ( 2nd opinion) and deal as above mentioned.
Hope this information will help you.