Since letting your family know, getting professional help, and/or "letting it go" isn't an option for you, there really isn't much you can do except learn how to cope and deal with it.

I've had it my whole life and didn't even know such a thing existed until I descended into a major depressive disorder (with psychotic features), then everybody knew I had mental health issues, even those I was trying to hide it from.

Not trying to you out there, but any type of depression is nothing to mess around with and the sooner you get it out in the open and start receiving the professional treatment needed, the better off you'll be.

Sincerely,
Pfrog!