Cancer or liver failure don't cause those GAD antibodies. Testing positive for those means your immune system is attacking your insulin producing cells, hence T1 for sure.
Anyone can get cancer of course, with or without diabetes, but the chance of coincidentally developing T1 diabetes and cancer at the same time is ridiculously small. The one thing has nothing to do with the other.
But if you're this worried, please contact your doctor and tell them about your worries. They might well be able to explain why they know you do not have cancer, easing your fears.
In the mean time, you'll have your hands full with learning to manage your diabetes, wish you all the best with this as well, and please ask away on the forum!