Let's start at the beginning. You carried the torch for this man for eight years before you became intimate. Wow. On one hand, I want to congratulate you. A lot of the girls I had crushes on, I never got close to. But I think you had unrealistic expectations when you did have sex with this man. I believe that you thought that the sky would open up for him, and he would fall deeply in love with you. And when that didn't happen, you let your insecurity take control of you.
Now this man didn't run away from you. He didn't even back away immediately. He was merely taking some time to process his feelings. I know, that sounds like bullshit, but it's probably true. Some men don't come quickly to a realization that they are in love with a woman. They have to mull it over and deny it to themselves for a while before they can come to a realization. Not the most mature behavior, but what can you do? That may have been what was going on here.
At least until your outbursts, accusations, and overly suspicious behavior worked to drive him away. I agree with Garland that you just didn't "pass his office" that day. You were checking up on him. Own your stalkerish behavior. And I think it's safe to assume that he found out about it, too. After all, he's paying that secretary to look out for him, and that includes, unfortunately for her, acting as a buffer between him and suspicious girlfriends while he's at work.
Can you get this relationship back together again? Yeah, anything's possible. But frankly, why he'd want to, I don't know. He may really have feelings for you, after all. But my advice, if you two do try again would be for you to grow up and calm down a little, not try to force things, and let them grow naturally on their own. Thanks for the question.