If a shy guy gets a letter from a girl letting him how she feels how will he react?

I really do like him and i feel that he likes me too but he hasnt replied n its almost a month now so now i feel that he doesnt so i just wanted to know wat i should do cause the last thing i want is to lose the frndship ,i just followed my heart n wrote that letter cause all i wanted was for him to know how i felt...now i feel it was maybe a mistake n im not good any getting signs from a guy n its the first time i really do like someone :/ we have become quite good frnds n thats y i thought i should just let him know.