I recommend visting the Relationship forum on here. There are some stickies about Relationships and Codependency that I have found EXTREMELY helpful.
There is a list of what a Healthy Relationship is vs. Toxic Love.
I feel less alone reading your post. I, too, am an obsessive, nervous thinker in terms of men. I found it EXTREMELY difficult in the beginning to maintain my newfound independence and still allow a man into my heart. I had not ever cultivated healthy responses to things in arelationship. I only attribute this to the fact that I have relied on men in relationships to give to me emotionally what I could not give mysefl. Very sad. If you ever need to talk or to write about your obsessing- feel free to private message me.
My advice is to always take relationships slowly- the faster they move, the more likely I find myself slipping back into dependent behaviors and losing my identity.