Sometimes people think that you've got to have absolutely horrible problems before you can go to a therapist, but that's not true--it's like saying you can only go to the doctor if you've got a compound fracture; you're not allowed to get treatment for a sprained ankle. Therapists can help people even without mental illnesses--people just going through stressful times, like they've lost somebody or they're arguing with their family or whatever. It's perfectly legitimate for you to go and say, "Well, this doesn't actually cause distress, and it isn't interfering with my daily life; but I want to learn more about myself, and you've got training in psychology, so..." Nothing wrong with that. Therapy for the purpose of insight and self-improvement is not a bad idea, especially when you have the tendency to form alters. Maybe you can learn more about why you tend to do that.

As for the question of whether they're real: Yes, of course they are. They're as real as your thoughts, your feelings, your memories. Whether they are full-blown alters--who knows? That's one of the things you could talk to a counselor about, if you decide to go to one. You'd know better than I would. But your experiences are legitimate, by definition. What you experience inside your head--your thoughts and perceptions--is as real as any other idea or thought. "Is it real?" can be answered in the positive. But the more interesting question is, "How will I interpret this? How will I act on it? What does it mean to me?" Those may take a while to answer, but that's okay. There are far worse ways to spend your time than thinking about how your mind works and why.