It sounds to me as if your doctor is okay. He's probably asked you to make an appointment so that he can discuss your test results with you - I hope so anyway!
If it is diabetes, then you've been diagnosed and your treatment will begin. If it isn't, he'll have to consider other options, so he still needs to see you again.
Make sure he tells you what tests have been done, and what the results mean. Take your time and ask any questions you can think of - there's a list on here somewhere, if I find it I'll come back and tell you where it is.
Also, if he's asked for an HbA1c to see how your blood glucose levels have been averaging over the last 3 months, that test does take a little longer for the results to come back. It does here, anyway.
Diabetes is a d**n nuisance but it's not the end of the world, even though I should think every single one of us thought it was on diagnosis! You'll feel better when you know what's wrong. Diabetes can be controlled, and you've come to the right place for really good help and support.
Let us know how you go on. Best of luck!
Viv