It's not fair to you. You have a valid reason to leave - after all, this is not just about the lack of sex. But if you want to stick around, you need to convince him to get help.
i guess its up to you if youre willing ot stay and convine him/wait for him to get help regarding this, or if the need is great enough for you to break up and move on. is it stress thats killing his libido, or sexual abuse in the past, or something else entirely? we dont need super specific details but a little somethign to work off of could tailor the advice/who he shhould see/what he can do a little bit more
Try to get him some help with his depression. If you don't want to go through all that work then it probably means you are over the relationship anyway.
