You may not believe me, but I've never tried ...
This may seem hard to believe, but I've been to ...
As amazing as it sounds, I haven't seen ... yet.
You won't believe this, but I've just ...
This may seem hard to believe, but I've never liked ...
This may sound unbelievable, but I've ...
You may not believe this, but I've never been to ...
You'll never believe this, but I've always liked ...
I know it's hard to believe, but I've never ...