With your second sentence, "There is no greater pain than loosing a child", you should replace "loosing" with "losing"... that is the correct spelling of the word that you are trying to use. Other than that, everything else looks good! :)

The first sentence and the last sentence are correct. The second sentence should read as follows: "There is no greater pain than LOSING a child." "Loosing" is not a word. However, LOOSE and LOOSEN are. LOOSE is the opposite of tight. If something is too tight, you LOOSEN it.