By what definition of "sentience"? Wikipedia claims "Sentience is the ability to experience feelings and sensations" as an opening statement, which I think would be trivial depending again on your definition of "experience" and "sensations". Can a LLM hooked up to sensor events be considered to "experience sensations"? I could see arguments both ways for that.
I have no way of measuring whether or not you experience feelings and sensations, or are just regurgitating statements to convince me of that.
The only basis I have for assuming you are sentient according to that definition is trust in your self-reports.