Had a look at some of KidderminsterKate's previous posts.
You are a bit difficult to read on here really.
I have some questions, but you may not wish to answer them.
Do you work full time. Looks like you do.
And if you are eligible for those tax credits, which you may be for all I know, then yes, it is up to you what you do with the money.
I would question the nose job though.
I think you may be wanting to do it to be more popular/have more friends, but that often isnt the way to do it.
You may feel better initially, but it may not be the answer you are looking for.
As I said before, if your self esteem is low, that may be better to try and build up that instead.