My friend I am so sorry. There are so many people here that know the same pain. I have felt the same pain as you. My friend you are feeling grief. And that is okay. Grief has many symptoms and you feel not yourself and abnormal going through these things. I myself could not eat for weeks, and could not get out of bed (I had to take time off work).
I am sorry - the future you had dreamed of with this person is no more. This may be what you are grieving. I know this is a painful thing to face. And can sometimes end very suddenly or badly. And this is so traumatic. It is an emotional truck hitting you full force.
With Grief, unfortunately, you must move through it and face it head on. Being alone after being with someone for so long is awful and I know you feel like you lose part of yourself.
What helped for me (these thoughts/ideas/solutions came from therapy)-
Cry. Even if you have to spend all day crying. Cry into your pillow, cry in the shower. Cry on the way home from work or school. Wherever you can get privacy. Get the sadness out of inside of you. My ex wasn't always a bastard but I would often call him that when I cried because it all felt so unfair. These extreme things are just ways of us getting through grief. By the way, people telling you to 'move on' can eat shit. You move on when you are ready.
When you think about the other person and reminisce on sweet memories, and this will sometimes come randomly doing something, it can be anything this is normal, however you must also remind yourself why it ended or wouldn't work.
Use music. Believe it or not, 70s-80s disco, and 90s dance got me through my last breakup, lol.
You deserve love my friend. Never forget this. One day there will be someone out there for you, when you are ready to make room in your heart for them.
Self love - take extra care of yourself during this time. Drink water, buy some epsom salts for a bath if you have one, use some essential oils, whatever you define as self care. Or you can google for more info on this.
Don't use alcohol or drugs. Don't. This will only delay moving through the grief (emotionally numb you) and make you feel like shit the next day. Ask me how I know.
Think about what you can learn from the ending of this relationship so you do not bring baggage into the next. What was it about them that was incompatible with you? What could you have done better? Did you miss things in retrospect? Do you need to work on your communication style? etc
In terms of spirituality, I would often pray to Satan and Aphrodite, asking them why, you know. Letting them know I felt wronged, or that things were unfair. Like a prayer journal almost. And simply asking them to help me through this painful time. To help me find someone who loved me for who I am, and wanted the same things as me.