What Causes Coughing Fits After Taking Mucinex?

Hello, so on the 18th, I was bed ridden. I slept in super late and whatnot cause I felt super groggy. I was also coughing super bad, so my brother suggested I take mucinex. So I did and fell asleep. I woke up the next day feeling so much better. So I went to work feeling perfectly fine until like 20 minutes into it. That's when I kept getting the feeling that I couldn't breath and I kept having uncontrollable coughing fits. Like, no matter how hard I tried to suppress it I couldn't. And it was also deep seated coughs. I could feel it in my chest or something. Then that night I literally got no sleep because I was coughing so bad. None of the medicine I took worked which was mucinex (again), benedryl, and tylenol. So the next day I called out of work cause I didn't want the same thing to happen where I have coughing fits, that and I got no sleep. And it's been lasting till today. The front of my rib cage where they connect is sore from coughing so much, and it gives me excruciating headaches. It's definitely not a dry cough, but at times it is. I just feel like I need to keep coughing so I can get whatever is in my lungs/ throat out. But I can't. What do you suggest I do?