Can you get serotonin syndrome from Prozac and DXM?

I took 90ml of cough syrup and Ive been on Prozac 40mg for 4 months now. I feel like ****. Im seeing things out of the corner of my eyes, I have a headache, nonstop stomach pain, constipation, and now I feel like im on the verge of having a panic attack, I havent had one since I started taking the Prozac. A new symptom that just developed is ringing in the ears. Help? Anyone :(