As someone who dated someone just like you, and just lived this situation, I can give you some of the very best advice.... Get help. Your depression and disconnection is not going to let you be a good partner, no matter how substantial your realization of love for her may be. You want to show her you love her, then you need to get yourself healthy, you need to get to a place where you can love her. Seek help from a professional, get your head right before you engage with her, get to a place where you love yourself first. I know it sounds cliché but it's very true. Love isn't enough. Long term relationships are about being a loving, healthy partner and you can't do that from a depressed state. You can do that, and you can even let her know your intent, but focusing on being her mate rather than pining for her love will help to get you where you actually want to be.

I've done this journey with my SO, and it was incredibly hard on me. I almost wish I had ended it the way she did with you, so he could go off separately and get healthy. Atleast that way I couldve gone without all this damage done to myself in the process. I'm proud of what we managed to accomplish, but in the end we just couldn't overcome the past damage. Be smarter than us. Do this right; If you really love her then it will be worth the work and the wait.

Lest I not forget, you have to decide to do this for yourself first and foremost, otherwise you will find it easier to give up at the slightest turn. Good luck to you, dear. I'm sorry this is happening.