“我疯狂的爱你”

I had a crash on you...

绝对没有语法错误（不过这个更表示单方面的爱）

如果还有问题可以百度Hi我

I love you crazily

or you can actually say "I love you crazy", technically not grammatically correct, but it's accepted.

i have a huge crush on you 美国式的
i love you insanely 或者 i love you without sanity 中国式的

I am crazily in love with you.
I'm crazily in love with you. (比较口语化)

比较常用的是:
I'm madly in love with you.

都可以，语法绝对正确。

I'm crazy about you.

I'm crazy about~