And he is still on my mind so much. I feel like I am on the verge of tears. I guess the ups and downs are to be expected...
Of course he's going to be on your mind. Of course it's going to hurt like hell. He's important to you, and he'll likely occupy a particular place in your heart for a long time.
This is the price we pay for being human and for having the capacity to love others.
You will get past this, in time. Who you'll be when you come out the other side of this remains to be seen. But I'm guessing you'll be wiser and stronger when all is said and done.
Hang in there.