I know you've tried to help me, and I'm frustrated that I can't express myself fully.
"I know you've tried to help me, and I'm frustrated that I can't express myself fully."
「せっかく手助けしてくれたのに、言いたいことがうまく伝えられず歯がゆい」
* try to help: 助けようとする
* be frustrated: 歯がゆい、もどかしい
* express oneself fully: (言いたいことが)しっかりと伝える、完全に伝える
ご参考になれば幸いです。