I think that I don’t fit him,because I have a dark past.I talked to him about my past.
and he enocouraged me about my dark past,but I think about him and become anxious.
私は彼と似合ってないと思う、だって私には暗い過去があるから。彼に私の過去を話したら彼は私の過去を受け止めてくれたけど彼の事を考えると何とも言えない気持ちになる（不安になる）

他に何か良いいいかたあったら教えて下さい。
よろしくお願いします。

I don’t think I’m good for him, because I have a dark past. I’ve told him about it, and he understood it, but even still I feel sorry.

ちょっと内容が変わっちゃうかな？ 　

I feel I’m a lousy match for him because of my dark past. He was understanding when I told him about my past, but every time I think about how he must feel, I still get overwhelmed by anxiety. 　

「暗い過去」って本当にdark pastなの？
silly experiencceくらいじゃなくって？