Hello
As you mentioned that this pain is from last 4-5 months , typically after meal ( mostly ) , this type of pain may be due to these reasons , these includes.
1 Hyper acidity or
gastritis or
Hiatus hernia or
Peptic ulcer disease , as all these are nearly same , so need not to worry about name . Diagnosis can be confirmed by upper G I
endoscopy. Try raising the head of your bed about 4 inches with blocks. It might also help to avoid eating or drinking for 2 hours before you lie down. To help 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 if pain is severe you may need drugs like
proton pump inhibitors ;like pantaloc-D once or twice in day.
2 As you mentioned that pain is near waist line and also radiating in the back , so this may be due to renal calculus . Diagnosis can be confirmed by
ultrasound of both kidneys .
3 Amoebic colitis is the another most common cause of this type of pain . Diagnosis can be confirmed by physical examination by a physician . Stool examination also find entamoeba histolica .
In ,my opinion consult a physician and get his opinion as above mentioned above.
Good luck.