Sigil Formating? Text won't wrap.

Hello,
I recently compiled my ebook in Sigil, but before I publish the work I ran it through Amazons Kindle Preview Emulator to see what the final product would look like. The problem I'm facing is that the text doesnt wrap around to the next line correctly. Where the text ends on the right of the Sigil window, in the emulator it single spaces to the next line and ruins the layout.

For instance I could have

"The boy from Oklahoma bought a plane and decided to drive race cars instead.

But then he decided to go to the mall and buy an icecream."



Which turns into

"The boy from Oklahoma bought a plane and decided to drive
race cars instead.

Bit then he decided to go to the mall and buy an icecream"



Any suggestions?


Best
Stephan