Sounds okay untill you get to the bridge. Maybe work on that?

Strum pattern?

Should check out my version of this song. It's in the proper key.
http://www.ukulele-tabs.com/uke-songs/jason-mraz/i-won-t-give-up-uke-tab-21635.html

Are you sure to use Bm? Maybe its correct, but its not working for me..