How to lose a stubborn pot belly.?

I have a pot belly and idk how to get rid of it. It is very annoying and all I want to do is get rid of it. I have tried exercising, eating different, and even taking omega 3 pills but I am not seeing any big changes. What should I do? And I do sort of have an awkward posture and when I stand up completely upright, my protrusing stomach does go away a little bit.