What Is The Treatment For Extreme Depression?

Sir i lost my mom in 2012 and she is the only person whom i close with my father is not live with us .. After i lose my mom i met a boy whom i atach like i atch with my mom but he is also enGage with someone else so i am in a big deprsion right now .. I cant sleep he alwz roam in my mind plzzz help me out with this depression