I'm with SueZ and Montana.
Really, girl, you've gotta give up thinking about this guy and the best way to do it is stop contacting him and, when you start thinking about him, change the subject in your head. No one makes you think or feel anything, but note also that you can change how you think and react to situations. So if you want it to be over and done with this guy from work (and it sounds like you're ambivalent about that but he is not), job one is to get rid of his email, block any incoming messages from him (there probably won't be any, but you will feel better if you are proactive about this) and try not to run into him. That need not run your life, but the bottom line is, you are not helping things by harping on this.
Now, about your current marriage - quick question - how would things be if your current husband became disabled or died? Don't say it can't happen. Disabilities affect 1/5 of all Americans, see:
http://www.census.gov/prod/3/97pubs/cenbr975.pdf. So the idea that you can't be alone is, sorry to say (I'm gonna be harsh here) nonsense. Why, exactly, do you not feel capable? I suspect this is a feeling you should explore through counseling. Most people over age 25 feel at least minimal competency and this is especially of concern if you are considering having children. After all, if you feel you can't take care of yourself, you may find yourself overwhelmed by taking care of a child or two. So explore these feelings and work on resolving them. No matter what happens with your marriage, this will be of help to you.
And those feelings may lead you to leave your marriage. Or perhaps they won't. But ask yourself - whether you love your husband or not, ask if you are friends with him. Do you care about how he feels? Does his comfort level matter to you? If the answer to any of these questions is yes, you need to sort this out soon, before you have a full-blown affair which involves sexual infidelity - and your husband finds out (He will. Most of them do). Ask yourself if your fear of being alone is worse than how you might feel if you are sexually unfaithful and your husband finds out from someone other than you. Or how you might feel if he doesn't find out, and you carry the guilt around with you.
Oh, and another thing - leaving under your terms is a helluva lot easier than leaving because you've been kicked out. Amicable divorces beat divorces based on infidelity any day of the week.