「よく飽きないよなって思う」は英語で「I'm amazed (you) didn't get sick of me.」と言います。「you」は対象の代名詞を使ってください。「よく」の意外性は「I'm amazed」に入っています。
コロナの影響でほとんどの時間を夫婦で過ごすようになったけど、一緒に居すぎて、主人はよく私に飽きないよなって思う。
Because of the coronavirus, most of our time is spent together as a couple, but we're together so much that I'm amazed my husband didn't get sick of me.
・I wonder how he never gets tired of me.
・I can’t believe he hasn’t gotten bored of me.
・Sometimes I think, “He must be sick of me by now,” but he isn’t.
・I’m surprised he never seems to get bored of me.
英語では **get tired of ~** や **get bored of/with ~** が「~に飽きる」という意味でよく使われます。