Snake wont eat!

[bdemutis]

This snake has been a pita since I got him last year he was eating good only for the summer I got him in the winter last year I know they go dormant in the winter but I keep his tank around 80 on the hotspot side with a red light on all the time. I honestly think the last time he ate was September or October. He wont eat I tried multiple times the petshop owner told me not to worry about it her hog doesn't eat during the winter. But I'm worried about him I left a mouse in his tank over night with no success I just used tuna oil no success I even got him to open his mouth and stuck the head in and held it there and he just kept fighting his way off even after he sunk his fangs in he just let go. So I put him back in his tank and gave up I don't know what else to do I don't know if the pinky was to big for him but even frozen ones he wont eat.