You have gotten divorced. It does not matter that you were not legally married. A ten year relationship is a long one, as long as lots of marriages. On the up side, you're not having to go through all the legal hassles of a divorce. On the down side, you don't have the protections of having been legally married.
Do NOT take that as a judgement. You were in a relationship. For whatever reasons you didn't go through the legal stuff of marriage. The emotional stuff is still there, and that's what I (and others here) are addressing.
You need to understand that you have to move on. It's very hard. Really. Very hard. Did I mention that it's hard?
You have every bit -- maybe more -- of the emotional work of someone who was conventionally married. Only you don't have the societal and legal support.
Give yourself the time to grieve. To be angry. To have regrets. And then, pick yourself up and work on starting over, of establishing your own life anew. I'm not going to give you a timeline, but I am going to point out that it's realistic to start moving on meaningfully after a year or so. If you happen to need more time, that's okay. But if three or five years have passed and you're still stuck emotionally, consider getting professional help.
Moving on is not easy. I've now been divorced for five years. My ex left me for another woman, and there are some aspects of that I'm still not completely over. The important thing is that I've established a new life for myself. I chose to move 800 miles away to a new city, and while it hasn't been completely smooth, it's been good. I have a new life.
It's my firm belief that everyone can have a new life. The details will differ from person to person, but it's completely possible.
Let yourself hurt. Let yourself wallow in this as you need. Personally, I found that a bottle of wine many nights was quite useful. Do what works for you. Eventually the strongest emotions will fade, and you'll move on in our own way.
Much love and support.
SheilaT