Uncomfortable sensation in R eye. Eye?

I am breaking down into the points :- 1. My right eye feels somewhat weird. There is uncomfortable sensation / mild pain within the eye or maybe can say behind the cornea it feels. 2. Recently I had an eye exam and it was normal. Eye pressure was normal too (16). But there is a refractive error of -0.5 cylindrical in the right eye. I was also given comfortz eye drop for evaporative problem. 3. Whenever I wake up in the morning , there is dilation of blood vessels visible in my right eye. Those red veins like structures become prominent and red. What do you think is the reason behind the discomfort of my eye? 4. I also suffer from post nasal drip associated with allergic rhinitis for which I take modern antihistamines like Cetirizine and montair LC (montelukast+levocetirizine). Do you think that nasal congestion or inflammation of nasal membrane has to do anything with it OR if these meds cause dry eye which is causing symptom. But why only right eye??? Left eye feels completely fine.