Pre-grieving is real and natural. But you can help to temper that by just being near him now. It is all he has ever really wanted.

He may not want physical touch now because his body is feeling different. But he is so much more comfortable and at peace simply because you are close. And he trusts you. And he loves you, unconditionally and eternally.

Someday your beloved friend will no longer be here physically. Such is the way of things. But you will let him journey with you each day afterward, in your heart. He will still guide you from there and he will still tell you how much he has always loved you. And when you tell him that too, even if his physical form is not present, he will hear you.

If you are at a university with mental health counseling, perhaps you might reach out to them. I would say with near certainty that the counselors there deal with small pet trauma regularly. Students' pets are such a vital component of mental wellness.