I know you're busy but it hurts when I can't see nor get in touch with you
I know you're busy but it hurts when we can't see nor get in touch with each other
I know how busy you are だと どれだけ忙しいのかは分かるけど
の意味なので I know you're busy の方が良いと思います。
「…会えないし連絡さえ取れないのは…」
" ...when I can't see nor get in touch with you..." など
後者の when we can't see nor get in touch with each other は
複数形の二人称です。
「…辛い」
"...it hurts..." など
日本 
