What Causes Acid Reflux Along With Burping And Chest Pain?

Hi I’m 22 and have been experiencing heartburn symptoms for awhile, but it’s gotten worse in the recent years. I have taken treatments and they work to relieve me of my burning and problems burping, I also ecperience chest pains and shoulder pains. I recently stopped taking nexium after about a month, even though it helped me feel normal again, except for sometimes a throbbing sensation in my chest and black stool. I was worried about the stool because I know it can mean dangerous things. So to make sure it wasn’t that I stopped taking it. After a week my symptoms returned but throughout the week I didn’t have black stool and I was wondering if I should keep taking it? If that was a symptom of the medicine? Or what?