Which over-the-counter eye drop can i use for conjunctivitis?

None really: Most "pinkeye" or conjunctivitis is actually viral, so eye drops, including antibiotics, are usually not effective. Viral conjunctivitis tends to run it's course in 7-10 days. It can be very contagious, spreading from one eye to the other or to other people. Hand washing is essential. To be certain it is not a more serious bacterial or fungal infection, you should see an ophthalmologist.