I think that what has happened to you is very unfair, but you have to go on. My girlfriend commited suicide two years ago, I didn't forget that, but learnt to deal with it. And I became gay...
Accept the fact it has happened and you'll be okay,
just think of how many people lose someone who is dear to them and they survive, they can get on with their own lives, not immediately but in time. Remember this and you're on your way to start the grieving process.
Don't lock yourself up, but take your own time.
As you need it...
We all have bad times, and I'm sorry yours is now, but think about the good moments you had with her.
That helped me a lot. Hope it helps you somewhat...
All my best to you!