I totally feel your pain, its really hard when someone you trust so intimately manipulates and uses you like that. I feel that you might be in such a shock, and grieving.
Not long ago, I went through something similar.
Some days, many days, I look around and even in children like you say, I can see these deviations from the light. Its part of living in this world and we cant change others, which makes me so angry because I cant accept it.
The worst is realising that even animals have more heart and more love in them than most of us.
I could tell you to look around for random acts of kindness, people everywhere fighting for a better world and to save each other, to save animals and the planet. You know they are there.
But when you are feeling this way, in my experience its better to allow yourself to go through this darkness and acknowledge your pain. It is ok to rage and become bitter, to cry and withdraw, you must be feeling so raw right now.
Slowly, but surely you will feel better, and although there will be days when you want to strangle everyone around you, there will be reasons to go on and believe in people and in love again.
Trust me, Ive been there so many times.
Dont give up.
Love and light your way. x