First responce pregnany tests?

my pireod ended April 12th i may hae conceived the 15th. what is the earliest date i can take a early detection pregnancy test. and if i am preggo i will be a single mom and would love for some info on sites to help me threw this. im 26 and have helped raise 5 kids in the last 5 years so i know some of the things to expect. thank u.