Expressing reconsideration at the end of a sentence.

[Thanos]

Can I add "I hope." or "I think." at the end of a sentence? Is it considered proper english?

e.g.:

Bill Clinton can play the guitar. I think.
I will have no problem sleeping early tonight. I hope.

My mind goes blank and cannot figure this one out. Intuitively it sounds fine to me but I can't tell if it's the English student or native Greek in me issuing the confirmation.

Of course I am talking about speaking or informal writing(e.g. forum posting, friendly messages,etc.).

[Jamie (K)]

Yes, you can do it.