Emergency contraceptive pills are effective 2 hours after sex? is it not too early?

They're effective : Yes, they are effective at that time.

If an emergency: contraceptive pill is needed - that is an ideal time to take it - as soon as possible after sex. Plan B One-Step is up to 89 % effective when taken within 72 hours (3 days) after unprotected sex. It can reduce chance of pregnancy by up to 95% if used within 24 hours. It continues to reduce the risk of pregnancy up to 120 hours (5 days) after unprotected sex, but is less effective as time passes.