I am not expert in this matter but here is what I found on some blogs how you need to structure your SSML to insert breaks, including those at the end of a line or paragraph:
<speak version="1.0" xmlns="http://www.w3.org/2001/10/synthesis" xml:lang="en-US">
<voice name="FlorianMultilingual">
This is a text.
<break strength="strong"/>
This is a text after a break.
<break strength="strong"/>
</voice>
<voice name="FlorianMultilingual">
And this is a text in a new line, after a break at the end of the previous line.
</voice>
</speak>
or use time in your break tag :
time="2000"