Thank you for the additional information.
The fact that you are slim increases the likelihood that you have diabetes type 1.5. It would be more definitive evidence that someone has diabetes type 1.5 if a medicines that work by improving insulin sensitivity, such as metformin, does not work to lower blood sugar. There may be an initial partial response to metformin, but it is not sustained. Since you had to stop the metformin because of side effects, you were not on the drug long enough to differentiate the types of diabetes.
The sitagliptan works by a different mechanism than metformin, and there is evidence that it can help people with diabetes type 1.5, as well as people with diabetes type 2.
There also are some blood tests that can be done. Diabetes type 1.5 appears to have an autoimmune component, and checking antibodies against the islet cells of the pancreas (where the body makes and releases insulin), can help to identify those people with diabetes type 1.5.
So, with your height and weight, there is a good chance that you have diabetes type 1.5, but the blood sugars and the diabetes medicine treatment history do not prove it. However, you can discuss checking islet cell antibodies with your doctor to help to clarify the situation.
If I can provide any additional information, please let me know.