Guaifenex and chest pain

I went to the doctor and he said I had the begining signs of an upper respiratory infection. He put me on this medication and told me it would help with the sinus pressure. Since I have been taking this medication I have had increased chest pain, coughing and sore throat. I decided to stop taking it this morning to see what would happen if I used just a regular sinus pill, and I actually felt better! I took one more dose of Guaifenex and I am right back where I started 2 days ago, feeling misserable and I can't breathe. I dont know where to go from here?...Has anyone else had increased chest pain?

My doctor prescribed Guaifenex PSE 600 for extreme sinus congestion. I started taking the pills (1 every 12 hours) yesterday. Yesterday morning, I experienced really bad nausea & light headedness. I was able to breathe so much better, the drainage & congestion had really cleared up. I am not experiencing the dry mouth, nor sleeplessness, but I am concerned because this morning I am having chest pain. I'm a bit worried about continuing this medicine. It works soooo good, but don't think the side effects are worth it.