No_longer_sane,
Funny. At 16 I'm having those same maternal feelings. I've had that same despair of love and children. I've had those exact same thoughts about happiness, God and eternity.
But you said it yourself. Nothing lasts forever. Not even these horrible feelings. Not even this oppressive sadness. Not even this depression which weighs you down and sucks the life out of your spirit. You felt better. Believe that you can feel better again.
What's going on as far as help? Last I remember you were going to a doctor...? What became of that? Are you getting what you need to carry you through this? You are worth it.
Have some hope (It's free! Just requires a little care.) We are young. Things can still turn around- they can always turn around.
You're in my thoughts, No_longer_sane. Hang in there.