I feel terrible. 我觉得不舒服。
I have no get-up-and-go. 我觉得有气无力。 You're not coming down with something, are you? 你不会是病了吧。
He's kind of frail. 他的身体有点儿虚弱。 I'm numb I don't feel anything at all. 我全身都麻了,没半点儿感觉。 My muscles feel so stiff. 我觉得肌肉好僵硬。