I Get Liquid Diarrhea After Every Time I Eat A

I get liquid diarrhea after every time I eat a meal. I cannot gain a pound and am under weight. 5 ft 8 in 105 lbs. I am a very big eater. I've been thin all my life but never had these stomach problems. My stomach also gurgles a lot, last yr or so and I have excess gas. My stomach used to feel bloated after eating and then I would push on it and it would start gurgling like the food was moving thru. I had a colonoscopy and they say I have gastritis. Negative for cancer and H-Pylori. The GI Dr prescribed me Omeprazole and MD Dr prescribed me Dicyclomine. I no longer take either cause too many side effects and one of them is also diarrhea. Don't need extra of that!! Would gastritis cause these bathroom problems I am having? Seems like the food comes right back out the other end, not very long after eating.