Do I have an attachment issue?

You may but it doesn't really sound like it to me. You may be less affectionate than others in your family but that doesn't mean you have an attachment issue. I know a lot about attachment disorders and generally the symptoms are more pronounced. Your dad took a class and now he's an expert? If he really thinks you have an attachment disorder then he needs to help you find some counseling but if you are basically happy and well-adjusted, don't borrow trouble.