Why can I only send iMessages to my wife and nobody else?

IMessage isn't working. the only one i can do iMessage with, is my wife.

my friends who i know for fact they have iPhone i cant iMessage them- it goes out as SMS . but when they reply theirs come as iMessage.

I had reset network. do all the tips and tricks that i could find---Nothing.

i even when ahead and did a factory rest on my iPhone ( didn't back it up :( so i lose a few contacts hehe) and nothing.

now i dont mind no sending iMessages, but when some one do send an iMessage it goes to my iPad or iWatch no to my iPhone.

Any idea how to fix this ?

thank you

[Re-Titled by Moderator]