There are many routes to recovery...
Counselling, psychotherapy, a 12-Step meeting, rehab, telling a close family member, coffee with a friend... embrace as many ways of getting healthy as you feel you can at this moment. Building a solid support circle is the long-term way to move on from any addictive behaviours and dependencies.
Taking that first step can sometimes feel scary - like stepping into the unknown - and I will help you find a more stable, confident sense of yourself, so that you can keep your options open.
How come you allow him/her so much head-space?
Inter-dependency is largely happy and healthy - the ebb and flow of being together. Co-dependency, however, is unhealthy, often ugly and, as Codependents' Anonymous (CoDA) says, "...is a most deeply-rooted, compulsive behaviour."
There's no one single definition of Codependency, though it collects many labels: symbiosis, attachment style, trans-generational, etc. All and none define Codependency. It is, however, better viewed through its familiar 'cluster' of behaviours - though not everyone has all the behaviours, nor the same ones.
I've got you under my skin...
Codependency is a dance for two (or more) - you need the 'other'. Unfortunately, those who behave co-dependently are attracted to (and are hooked by) others who behave co-dependently. Behavior tends to polarize into Dominant or Compliant. They do look different, but both have the same fundamental needs: needing the other to fulfil something… be different… make something (from the past) better.
Constantly blaming the other and wanting them to change are key indicators, as are over-tight or very wooly boundaries, which get trashed or flexed to snapping point. Why doesn't one simply leave the other? Those who suffer from co-dependency will tell you that it is like being bound by an invisible umbilical cord.
Many people living (directly or indirectly) with those who have more obvious addictions or dependencies, can also behave co-dependently. For example: over caring, excessively trying to please others or placate situations, laying aside one's needs in repeated attempts to meet the needs of the addict/dependant - even using them as a scapegoat. It is common amongst spouses or partners, parents, brothers and sisters, children - even friends and workmates.
Codependency often sits underneath other, more 'obvious' addictions/dependencies. Many people who have successfully given up, for example, alcohol or drugs, may find that they still create the same unhealthy relationships - which is enough to make you want to pick up the old addiction/dependency again!
Take heart! Co-dependency is treatable - you really can move on from it.