Depression Vs love

Depression is a horrible thing to watch someone you love go through being unable to flick a switch to make them feel happy again makes me feel powerless. Happiness is something you want for the ones you love & plan to spend the rest of your life with. I know how bad depression can be as I've suffered from it in the past, I've just never watched someone I love go through it & I'm feeling helpless! Any tips of ways to help me feel secure as my SO pushes me away without meaning too. He tries to do the right thing by us both but is struggling with life & work at the moment. When he pushes me away I feel rejected, I am not normally a needy person but I feel like I'm extra sensitive as I'm worried about him, I love him so much & I feel like I'm loosing him to himself. I feel like I need to step back & tell myself he loves me and as he's doing the right things to get his mental health back into shape, I've just got to have hope & hang in there....   We were so happy together before, very in love & full of playful laughter & affection. I just want my best friend back. Hope is carrying me at the moment... 
Am looking for any KIND advice for anyone who's been in similar circumstances, positive comments only please... 
Xx