I don't really believe in it, but I worry about it a little.
I'm not that superstitious, but I guess it plays on me a little.
この場合、次のような言い方ができますよ。
ーI don't really believe in it, but I worry about it a little.
「それをあんまり信じてないけど、少しは気になる」
ーI'm not that superstitious, but I guess it plays on me a little.
「そんな迷信深くないけど、少しは気になる」
superstitious で「迷信深い」
to play on someone で「人に影響を与える」
ご参考まで!