Fortunately for me I can't recall any time I wouldn't be able to feel emotions of some kind. I am very much in touch with my emotions and usually identify them easily. But I've known people, who like you, are detached from their emotions. It often happens to those with a very traumatic history. Detachment helps some people to disconnect from the pain that may feel unbearable if they start experiencing it. Medications help do just that. They numb people to their pain, and, in some cases, this could be life saving, while in other cases, it can make the problem worse.

In any case, I suggest you to tell your therapist exactly what you told here, that you are not in touch with your emotions and can't identify them or even tell if you feel anything. It should give him (or her?) something to start working with.