I don't know you, or him, so I'm not going to say he was or wasn't your soul mate. Whether or not he is, that is how you currently feel, and that is all that matters. I lost mine for about 2 years, and I constantly had people telling me how I should feel about him, no one has the right to dictate that. Our story was much like yours, in love at 17, on again, off again relationship. Then he was just gone, out of my life, I had to find out from someone else he had started dating his ex, and later that they we engaged. That was it, he was gone forever and I was left to pick up the pieces. Now I don't know if he's coming back, no one does, not even him. What I do know and can tell you, is what I learned during a time like this
First and foremost: He is gone. There is nothing you can do about it, whether or not he comes back, no one knows, not even him. Life does not stop. You CANNOT just sit and wait for him to return. Even if he does, you will be nothing more than an empty shell, a modern day great gatsby without Dicaprio. If you sit, empty and hollow, whether or not he comes back, you will live your life bitter and angry, either for leaving you hurt, or for never coming back. Either way, same ending.
Second, you need to find that spark of strength inside of you. All of us have it, right now it's dim and hard to find, but you need to find it. Do whatever it takes to find it, movies, music, working out, whatever. That spark is your true self and it's waiting for you. Focus on making that stronger, until it consumes you.
Find healthy ways of dealing with it. Drinking, drugs, binge eating, these are cycles, not solutions. Yes, you will feel better for a minute, maybe two, but in realty it makes it worse. All it does it as add shame and guilt on top of the hurt, it will not fix it. Find a hobby you've always loved, chase a career you've been too scared to go for. spend some time really focusing on what it is you've always wanted to do. Take him out of the equation. For instance, there was a particular band he hated, but I really liked. Because we'd spent so much time together, I hadn't listened to them in years. After I started listening to them again, and found I really did like them, and that little spark got a little bigger.
You ever hear of the term fake it until you make it? Yeah, thats your code for now. Get up, get dressed in a way that makes you feel good, empowered and beautiful. Just you, not him, and not anyone else. Even if it hurts, even if all you want to do is stay in bed, get up, you are worth it, go shopping by yourself, yes it's scary as hell to be alone. It may take hours to make yourself actually get out of the car, or you may turn around and have to try again tomorrow, thats fine. Just keep doing it. Now I'm not saying avoid the grieving, there are going to be times when it's so intense it will make you feel faint. Thats ok, it's natural and a part of the process. Just don't allow it to consume you. Cry, maybe watch a movie, curl in bed for a bit. Then, when your brain starts engaging again, when you've cried yourself out. Get up, get dressed and start again.
Admit to yourself that you may be alone forever, it's a scary thought, makes it almost impossible to breathe. It's ok, right now it seems like the end of the world, but it will get better. Don't go down that dark tunnel of fear. Now, I don't mean you'll never have another relationship, relationships are healthy, you just may never feel that click, or one day you may find out your true soul mate was just around the corner. Don't settle, EVER. If you're with someone who isn't your match, and they want to marry you or whatever, DON'T DO IT. It isn't fair to you and it isn't fair to them. You may be keeping them from their happily ever after. But do go on a few dates. I'm not talking tomorrow, or even a month from now, but if you see someone that might be worth the chance, why not? Be open and honest with that person, you may see they are the cure, or they may just be a band aid, you never know until you try.
Above all, you have to keep going. There will be days when the darkness consumes you, it will happen. There will be moments when you're out, maybe with friends and suddenly you can't take another step because it's all to much. Close your eyes, breathe, play a song in your mind that speaks to you, if that helps. Force yourself to take a step, and then another, count them. If you've gone two steps you can go three.
In time you may realize that he was not what you needed, or not, thats not important. Either way, you need to make this journey.
Now as I said, mine came back, it took a long time to heal what was broken, but it can happen. Funny thing is, We are both grateful for our time apart. We are both sure that we would have never made it through the next couple years hardships had we not had it. He had to fix what was broken inside of him, and I had to learn that I was a strong enough person. Yes, he is my soul mate, my everything, but he does not consume me. I used to wait for his every move, and expect him to save me, but I needed to learn how save myself. You need to learn to do the same. Just take one moment at a time, if you made it through that moment, you can make it through the next, and the moment after that. Don't give up, and don't give in, you can do this.