What is the possibility that you are scared of being hurt by a relationship. Possibly the longer you stay, or more you care the more paranoid of being hurt that you become. This paranoia cause your subconscious mind to begin to ":create" problems that aren't there so that you can rationalize putting your "emotional walls back up to protect that original fear of being hurt.

You will most likely solve this problem by exploring your past to find out when that first traumatic experience(or series of experiences) occured, and actually learning how to deal with that pain, rather than being scared of not knowing how to deal with it if it happens again.