Thanks for the query to H.C.M. Forum.
Ibuprofen itself causes Hyper acidity ( heartburn
or gastritis) while omeprazole
As ibuprofen +omeprazole both were simultaneously so there was misconception in your mind about omeprazole , rather ibuprofen was real culprit.
Any way here is one possibility of acute gastritis
or Hiatus hernia
this can be confirmed by upper G I endoscopy. The raising the head of your bed about 4 inches with blocks . It also might help to avoid eating or drinking for two hours before you lie down.
To help control the stomach acid, one should not drink alcoholor drinks with caffeine in them or eat chocolates or spicy or greasy foods.
Antacid help, if severe symptoms take proton pump
2nd complaint is mucus entrapped with feces so this might be due to amoebic colitis.
So consult a physician and get his opinion.