How soon is to soon to test

Omg.. so my peak day was two days ago. My boyfriend and I have been trying since jan... this month could be it. I'm feeling cramping... and I'm so anxious to check but scared to be disappointed. I'm a medical student and can do pg test whenever I want.. but how long should I wait? AF is due 3/18 but I'm praying she says away.. when should I test??