First off, it sounds to me like you are in pain and that it hurts you not to be able to understand what people mean by attachment issues. I am sorry you are hurting. Is it your T who told you that you have attachment issues and couldn't explain in simple, down-to-earth terms what it is?

I hate expressions like "attachment issues", "trust issues", "boundary issues" and other "issues", because they are vague, abstract and, therefore, are nothing but empty psychobabble that doesn't make it any clearer to the person who is suffering why they are suffering.

I know in general what professionals usually refer to when they speak of "attachment issues".

Usually, the expression refers to the disruptions of the normal developmental process in childhood formative years when the child is most dependent on the primary caregiver. Attachment to the caregiver is a natural thing since the baby is utterly dependent on the caregiver for his/her life. When the caregiver is consistently present and is reasonably attuned to the child's emotional and physical needs, the child feels secure in that relationship and that allows him or her to develop a healthy attachment to the caregiver.

A healthy developed attachment generally means that the person throughout their life, from childhood to adulthood, feels reasonably secure in relationships with other people. They are not afraid to make connections, to develop intimacy, to get close to others, and, at the same time, they don't need constant reassurance that someone will always be there for them. If they were raised in a relatively healthy environment, they have completed a normal attachment-separation stage and have developed enough of personal autonomy by their adulthood which allows them not to collapse when their significant relationships end for whatever reason. People who developed healthy attachments in their childhood don't go through their adult lives looking for mommy or daddy surrogates. In their significant relationships they experience break ups differently from those who didn't have a chance to develop a healthy attachment in childhood. They do feel pain of the loss, but they don't experience it as a total collapse of their world and, after some time, they are able to move on with their lives. People with the so-called "attachment issues" have difficulties forming relationships, being in relationships and dealing with the endings of relationships.

I can't possibly explain the whole attachment theory here because it's huge. The best thing I can recommend if you really want to get to the nitty-gritty of the subject is the book by Dan Siegal "The Developing Mind". This book is the best one on the subject IMO because it's based on extensive research and everything is backed by facts.

I hope it helps. As to your situation, I can't possibly tell you if your problem is "attachment issues" or something else, but I do have to say that if you heard that from your T who was unable to explain to you what it is in plain English and how it pertains to your case, it's very disappointing. Any time Ts use psychobabble instead of human language, it's a bad therapy because psychobabble doesn't allow a therapist to build a connection with a client which is crucial. From what I've read in your post, it sounds like, most and foremost, you need a compassionate listener as opposed to someone who just throws big words at you.