I have to admit that

[Liquinn3]

Are all sentences correct to mean "I have to admit that"?

(Along those lines anyway).

Quiero admitir que. (English translation: I want to admit that...)
Me gustaría admitir que. (I would like to admit that...).
Admito que. (I am admitting that...)
Debo admitir que. (I must admit that...).
Tengo que admitir que. (I have to admit that...).

Thanks.

[Rusty]

None are sentences. They are sentence fragments. :)

All are correctly written, except that each should end in an ellipsis just like your good English translations do.

You are using a single meaning of admitir in your fragments. Perhaps it would be a good exercise to look the word up in both languages. Different meanings exists. ;)