Guaifenex and antibiotic

I was given an antibiotic and Guaifenex 600, twice a day. It affected my urination pattern. I would have a need to go but in the beginning very little urine would come out followed by more but not near the force as normal. Afterwards, I would always have the feeling that I had not emptied my bladder. I thought something may have been wrong with my prostate. I drank a lot of liquid during this time. I stopped but continued to drink a lot of liquid hoping to get it out of my system. About one day after stopping, I urinated normally.
I took both for ringing in my ear and an ear infection. Neither helped my ear infection. I also experienced a headache which I usually do not have.