There is a good definition here: http://www.diabetesnet.com/diabetes_types/diabetes_type_15.php#axzz14Fzy1wug
They say type 1.5 is ‘slow onset type one’ – so you may initially be treated with tablets but eventually need insulin because the diabetes is caused by your pancreas packing up, rather than insulin resistance. So I’m guessing if you have always had insulin, you are certainly a type 1.